TST: Fixturize series/test_datetime_values.py
This is in reference to issue #22550
Hello @Anjali2019! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/tests/series/test_datetime_values.py`](https://github.com/Anjali2019/pandas/blob/085fccd24a039e38c8cecdeedd8051f279936506/pandas/tests/series/test_datetime_values.py) !

 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22966?src=pr&el=h1) Report
> Merging [#22966](https://codecov.io/gh/pandas-dev/pandas/pull/22966?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/03181f0569c8b1f93f620a2986b4f174f9b6179b?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/22966/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/22966?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #22966   +/-   ##
=======================================
  Coverage   92.19%   92.19%           
=======================================
  Files         169      169           
  Lines       50812    50812           
=======================================
  Hits        46847    46847           
  Misses       3965     3965
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.61% <ø> (ø)` | :arrow_up: |
| #single | `42.37% <ø> (ø)` | :arrow_up: |


------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/22966?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/22966?src=pr&el=footer). Last update [03181f0...085fccd](https://codecov.io/gh/pandas-dev/pandas/pull/22966?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
