BUG: read_excel trailing blank rows and columns
- [x] closes #41167
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

Not an expert here, but could you run asvs for read_excel? @phofl here are the asvs on my machine (asv run -E existing --bench ReadExcel)

engine | this branch | master
-|-|-
xlrd | 35.8±0.1ms | 36.1±0.1ms 
openpyxl | 166±3ms | 165±0.4ms
odf | 678±5ms | 692±4ms

The asv test data has no trailing cells, so we don't see a measurable impact. I also tested both branches on a sample .xlsx file with 1000 rows × 2 columns and a single formatted cell on row 0, column 2**14.
[blank_cell_XFD1.xlsx](https://github.com/pandas-dev/pandas/files/6418200/blank_cell_XFD1.xlsx)

master 2.84 s
this branch 48.9 ms
(both times best of 5) thanks @ahawryluk  lgtm thanks @ahawryluk 