MAINT: Drop pd.options.display.mpl_style
Deprecated in 0.18.0

xref #12190

(another nice short deprecation! 😄 )

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=h1) Report
> Merging [#16761](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/18f7b1ccee1c723cac7f23a16099d08c17ed0a91?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16761/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16761      +/-   ##
==========================================
+ Coverage   90.93%   90.94%   +<.01%     
==========================================
  Files         161      161              
  Lines       49282    49263      -19     
==========================================
- Hits        44815    44800      -15     
+ Misses       4467     4463       -4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.71% <ø> (ø)` | :arrow_up: |
| #single | `40.18% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/config\_init.py](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29uZmlnX2luaXQucHk=) | `95.96% <ø> (+1.56%)` | :arrow_up: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.33% <0%> (+0.09%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16761?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/16761?src=pr&el=footer). Last update [18f7b1c...242f5af](https://codecov.io/gh/pandas-dev/pandas/pull/16761?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/16761?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@aade74a`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16761/graphs/tree.svg?width=650&height=150&src=pr&token=eZ4WkYLtcO)](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #16761   +/-   ##
=========================================
  Coverage          ?   90.94%           
=========================================
  Files             ?      161           
  Lines             ?    49261           
  Branches          ?        0           
=========================================
  Hits              ?    44798           
  Misses            ?     4463           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.71% <ø> (?)` | |
| #single | `40.18% <ø> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/config\_init.py](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29uZmlnX2luaXQucHk=) | `95.96% <ø> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16761?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/16761?src=pr&el=footer). Last update [aade74a...b2e56f3](https://codecov.io/gh/pandas-dev/pandas/pull/16761?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 @jorisvandenbossche : Can this be merged? Thanks! @jorisvandenbossche : Also, thanks for patching the merge conflict! for such a small conflict in non-code stuff, the web interface is useful :-)