DOC: fix Sphinx parallel build error caused for `doc/source/getting_started/intro_tutorials/04_plotting.rst`
- [x] closes #53777
- [ ] [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 an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

This PR appears to correct the specific issue. Need to do a full build again to verify that no other similar issues exist.
Looks good to me: When I ran into #53777, I came to the same fix as you did. Additionally, `doc/source/user_guide/10min.rst` needs an `:okwarning:` too where on line 750 (before `plt.show()`).

That should fix this type of error for the docs.

What I'm wondering is this: Why is there no failure for the GitHub actions that build the docs? I tried to replicate the environment that GitHub actions use locally, but I still run into the necessity of having `:okwarning:`.

Does someone have an idea? Thanks @tpaxman 