Update the double quotes for the NA value to single quotes
- [x] closes #54107 (Replace xxxx with the GitHub issue number)
- [x] [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
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Hi @Tianye-Song, thanks for taking this on! Just a note for when you make this update that there are other functions that use this parameter whose docstrings may also need to be updated. 

Also, I noticed the title you have here is about adding single quotes instead of double quotes; however, I think the idea was to add double back-ticks to add code style formatting so that each is clearly a string literal. That may be what you meant but just wanted to confirm. Thanks again! /preview Website preview of this PR available at: https://pandas.pydata.org/preview/54136/ thx @Tianye-Song 