[DOC]: To remove extra `` to match :class: rendering requirements
Removing extra `` to solve rendering issues

- [x] xref #21564
- [ ] tests added / passed
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

@TomAugspurger , I am not really much acquainted to :class: reference. Do tell me If I am wrong in the inference of the issue.
I guessed that the parameters should be enclosed in `` not `` `` by looking at the following:
https://github.com/pandas-dev/pandas/blob/f1ffc5fae06a7294dc831887b0d76177aec9b708/doc/source/whatsnew/v0.24.0.txt#L66-L70