DOC: Remove unnecessary parentheses in `:func:` & `:meth:` role
- [x] closes #59662
- [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~ N/A
- [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.~ N/A
- [x] ~Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.~ N/A

---

The func & meth role's parentheses are unnecessary as Sphinx will add them to the rendered output.

```rst
.. bad
:func:`read_csv()`

.. good
:func:`read_csv`
```

We're introducing a new rule to the sphinx-lint ([issue](https://github.com/sphinx-contrib/sphinx-lint/issues/114) & [PR](https://github.com/sphinx-contrib/sphinx-lint/pull/115)) and, since sphinx-lint utilizes pandas doc in the CI, we'd like to also fix the issue in pandas.

Thanks @mattwang44 great to see a new sphinx-lint rule for this in the future