[DOC] improving the ExcelWriter docstring
- [x] closes #47526
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).


Thanks @noatamir. Mind posting a screenshot of this docstring after the change?  Here you go:
<img width="745" alt="Screenshot 2022-07-01 at 19 42 15" src="https://user-images.githubusercontent.com/6564007/176944732-5ed2a6b1-223d-4c7c-97e0-4c3f7a4ea3fe.png">
 Thanks @noatamir! (Failure unrelated) 