DOC: cancel replace's doc list item text bold effect
- [x] closes #43937
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit) for how to run them
- [x] Cancel replace's doc list item text bold effect, detail could see below.

From 
![image](https://user-images.githubusercontent.com/25895405/136691591-6aae6597-99e7-4ae4-bca6-1e7380b1cad4.png)
To
![image](https://user-images.githubusercontent.com/25895405/136691594-c2b14ad8-c761-49c9-9ba3-b1a472280df7.png)

