MAINT: Deprecate encoding from stata reader/writer
Deprecate the encoding parameter from all Stata reading and writing
methods and classes.  The encoding depends only on the file format and
cannot be changed by users.

- [X] closes #21244
- [X] tests added / passed
- [X] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [X] whatsnew entry

For 0.24 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21400?src=pr&el=h1) Report
> Merging [#21400](https://codecov.io/gh/pandas-dev/pandas/pull/21400?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/415012f4f38ca0cf41717c51e49bd2349cba09a8?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/21400/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/21400?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #21400      +/-   ##
==========================================
+ Coverage   91.89%   91.89%   +<.01%     
==========================================
  Files         153      153              
  Lines       49596    49597       +1     
==========================================
+ Hits        45576    45577       +1     
  Misses       4020     4020
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.29% <100%> (ø)` | :arrow_up: |
| #single | `41.86% <100%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/21400?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/21400/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.23% <100%> (ø)` | :arrow_up: |

------

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 @bashtage : How come your PR is closing #21244, which is already closed? It was the relevant issue. I had to defer the depreciation past the point
release 23.1

On Sat, Jun 9, 2018, 18:48 gfyoung <notifications@github.com> wrote:

> @bashtage <https://github.com/bashtage> : How come your PR is closing
> #21244 <https://github.com/pandas-dev/pandas/issues/21244>, which is
> already closed?
>
> —
> You are receiving this because you were mentioned.
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> <https://github.com/pandas-dev/pandas/pull/21400#issuecomment-395987007>,
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 I added a test and fixed the whatsnew thanks @bashtage  I cannot check right now, but I do not think that the sentence " The encoding depends only on the file format and cannot be changed by users." is quite true. If I remember correctly, pre-118 Stata files used, in an undocumented fashion, the native encoding, Latin-1 on Windows and MacRoman on OS X, I don't remember for Linux. Officially, special characters were not supported. 

I think there is a case to be made for the encoding keyword, but with old versions dying out I am not sure whether it is worth the effort.