CLN: Removed all occurances of `goal_time` and enabled linting for benchmarks
- [X] closes #23075
- [X] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] whatsnew entry

The following changes were made:

- All occurances of `goal_time` have been removed. Running `grep -rnw asv_bench/benchmarks/ -e goal_time --include "*.py"` should no longer return anything.
- The benchmark folder is no longer excluded in `setup.cfg`
- Removed one unused import in `asv_bench/benchmarks/io/excel.py` to pass flake8.

Hello @eriknil! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/algorithms.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/algorithms.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/attrs_caching.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/attrs_caching.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/binary_ops.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/binary_ops.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/categoricals.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/categoricals.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/ctors.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/ctors.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/eval.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/eval.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/frame_ctor.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/frame_ctor.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/frame_methods.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/frame_methods.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/gil.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/gil.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/groupby.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/groupby.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/index_object.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/index_object.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/indexing.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/indexing.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/indexing_engines.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/indexing_engines.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/inference.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/inference.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/csv.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/csv.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/excel.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/excel.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/hdf.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/hdf.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/json.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/json.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/msgpack.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/msgpack.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/pickle.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/pickle.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/sas.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/sas.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/sql.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/sql.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/io/stata.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/io/stata.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/join_merge.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/join_merge.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/multiindex_object.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/multiindex_object.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/offset.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/offset.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/panel_ctor.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/panel_ctor.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/panel_methods.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/panel_methods.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/period.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/period.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/plotting.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/plotting.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/reindex.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/reindex.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/replace.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/replace.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/reshape.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/reshape.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/series_methods.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/series_methods.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/sparse.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/sparse.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/stat_ops.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/stat_ops.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/strings.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/strings.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/timedelta.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/timedelta.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/timeseries.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/timeseries.py) !

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/timestamp.py`](https://github.com/eriknil/pandas/blob/015b2e685cca16b604cb0a2ef439a834dffd2f8d/asv_bench/benchmarks/timestamp.py) !

 thanks @eriknil 