CLN: remove python2 file encodings
- [x] xref #25725

Remove usage of ``# coding=utf-8`` pattern from code base.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=h1) Report
> Merging [#26196](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d74901b1a114d70244fb919e8de630fb53481b00?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26196/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26196      +/-   ##
==========================================
- Coverage   91.98%   91.98%   -0.01%     
==========================================
  Files         175      175              
  Lines       52372    52365       -7     
==========================================
- Hits        48176    48166      -10     
- Misses       4196     4199       +3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.53% <ø> (-0.01%)` | :arrow_down: |
| #single | `40.69% <ø> (-0.16%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/strings.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc3RyaW5ncy5weQ==) | `98.86% <ø> (ø)` | :arrow_up: |
| [pandas/io/formats/format.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvZm9ybWF0LnB5) | `97.9% <ø> (-0.01%)` | :arrow_down: |
| [pandas/core/accessor.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYWNjZXNzb3IucHk=) | `98.79% <ø> (-0.02%)` | :arrow_down: |
| [pandas/io/formats/csvs.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvY3N2cy5weQ==) | `98.19% <ø> (-0.02%)` | :arrow_down: |
| [pandas/core/internals/blocks.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2Jsb2Nrcy5weQ==) | `94.08% <ø> (ø)` | :arrow_up: |
| [pandas/\_libs/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL19saWJzL19faW5pdF9fLnB5) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/core/internals/concat.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzL2NvbmNhdC5weQ==) | `96.48% <ø> (ø)` | :arrow_up: |
| [pandas/\_libs/tslibs/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL19saWJzL3RzbGlicy9fX2luaXRfXy5weQ==) | `100% <ø> (ø)` | :arrow_up: |
| [pandas/core/arrays/period.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL3BlcmlvZC5weQ==) | `98.53% <ø> (ø)` | :arrow_up: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `99.36% <ø> (-0.01%)` | :arrow_down: |
| ... and [13 more](https://codecov.io/gh/pandas-dev/pandas/pull/26196/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26196?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/26196?src=pr&el=footer). Last update [d74901b...2da1c2a](https://codecov.io/gh/pandas-dev/pandas/pull/26196?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/26196?src=pr&el=h1) Report
> Merging [#26196](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/d74901b1a114d70244fb919e8de630fb53481b00?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26196/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26196      +/-   ##
==========================================
- Coverage   91.98%   91.98%   -0.01%     
==========================================
  Files         175      175              
  Lines       52372    52372              
==========================================
- Hits        48176    48172       -4     
- Misses       4196     4200       +4
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.53% <ø> (ø)` | :arrow_up: |
| #single | `40.7% <ø> (-0.15%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26196/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/26196/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.9% <0%> (-0.12%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26196?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/26196?src=pr&el=footer). Last update [d74901b...2da1c2a](https://codecov.io/gh/pandas-dev/pandas/pull/26196?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 thanks @topper-123 