DOC: Updating DataFrame.join docstring
- [X] closes #22897
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

Original work from @JustinZhengBC in #22904. The remote branch does not exist anymore, and I need to create this new PR to rebase.

Merging on green.
Hello @datapythonista! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/core/frame.py`](https://github.com/datapythonista/pandas/blob/da039f10ba3620dc7a0279a986a97efb289d8f5f/pandas/core/frame.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23471?src=pr&el=h1) Report
> Merging [#23471](https://codecov.io/gh/pandas-dev/pandas/pull/23471?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/528527b20f085524f484fef70dcde3c0b051782b?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/23471/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/23471?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #23471   +/-   ##
=======================================
  Coverage   92.25%   92.25%           
=======================================
  Files         161      161           
  Lines       51207    51207           
=======================================
  Hits        47239    47239           
  Misses       3968     3968
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.63% <ø> (ø)` | :arrow_up: |
| #single | `42.28% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/23471?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/23471/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.03% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/23471?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/23471?src=pr&el=footer). Last update [528527b...ebe5935](https://codecov.io/gh/pandas-dev/pandas/pull/23471?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 This should be ready to be merged.