DOC: indicate that `month_name` and `day_name` also applies to Series
- [ ] closes #xxxx (Replace xxxx with the Github issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

<details><summary>Screenshots from local docs build</summary>

![Screen Shot 2022-04-08 at 9 18 31 AM](https://user-images.githubusercontent.com/247555/162454615-fad5b7d3-eab3-4ed3-843a-5439a1015153.png)

![Screen Shot 2022-04-08 at 9 18 13 AM](https://user-images.githubusercontent.com/247555/162454618-8d2f4aa8-592a-400e-babb-0ff3d2dcd4c9.png)

![Screen Shot 2022-04-08 at 9 18 04 AM](https://user-images.githubusercontent.com/247555/162454619-767b8eb6-2fc0-4704-8a94-275d73697f0d.png)

![Screen Shot 2022-04-08 at 9 18 37 AM](https://user-images.githubusercontent.com/247555/162454608-bcfe81c1-33af-4d5e-ac7f-5545fdb48577.png)

</details> thanks @tswast  @meeseeksdev backport 1.4.x Something went wrong ... Please have a look at my logs.