DOC: Backticks missing in pandas.DataFrame.query
- [ ] closes #40375 
- [ ] tests added / passed
- [ ] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [ ] whatsnew entry

I also noticed that in the same sentence double quotes were missing, so I added those as well. 
thanks @sstiijn  See https://github.com/pandas-dev/pandas/issues/40375#issuecomment-797882281 for an improvement.