DOC: Add SSLCertVerificationError warning message for documentation b…
…uild fail

- [ ] closes #61975
- [ ] [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
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [ ] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [ ] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

`pre-commit run --files doc/source/development/contributing_documentation.rst` PASSED locally

Here is a screenshot of the changed section in Contributing to the Documentation, if you chose to merge.

<img width="825" height="360" alt="Screenshot 2025-08-02 at 10 34 19 PM" src="https://github.com/user-attachments/assets/7cf8297b-3781-42f6-b705-bb63f8fc90bb" />
 Thanks @jeffersbaxter 