CLN: Remove deprecated parse_cols from read_excel
- [x] xref #6581
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=h1) Report
> Merging [#26522](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ba48fc4a033f11513fa2dd44c946e18b7bc27ad2?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26522/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26522      +/-   ##
==========================================
- Coverage   91.75%   91.75%   -0.01%     
==========================================
  Files         174      174              
  Lines       50665    50664       -1     
==========================================
- Hits        46489    46485       -4     
- Misses       4176     4179       +3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.26% <100%> (-0.01%)` | :arrow_down: |
| #single | `41.73% <0%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/excel/\_base.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2V4Y2VsL19iYXNlLnB5) | `91.81% <100%> (-0.04%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97% <0%> (-0.12%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `90.7% <0%> (+0.1%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=footer). Last update [ba48fc4...8f619dd](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=h1) Report
> Merging [#26522](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/ba48fc4a033f11513fa2dd44c946e18b7bc27ad2?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26522/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26522      +/-   ##
==========================================
- Coverage   91.75%   91.75%   -0.01%     
==========================================
  Files         174      174              
  Lines       50665    50664       -1     
==========================================
- Hits        46489    46485       -4     
- Misses       4176     4179       +3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.26% <100%> (-0.01%)` | :arrow_down: |
| #single | `41.73% <0%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/excel/\_base.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2V4Y2VsL19iYXNlLnB5) | `91.81% <100%> (-0.04%)` | :arrow_down: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `78.94% <0%> (-10.53%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97% <0%> (-0.12%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/26522/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `90.7% <0%> (+0.1%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=footer). Last update [ba48fc4...8f619dd](https://codecov.io/gh/pandas-dev/pandas/pull/26522?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks @mroeschke !