PR Summary

Closes #23977. One can also check with the simpler example given at #23977 (comment).

Actually in the specific case of the eqnarray given in #23977 there would still seem to be an extra blank line at the bottom, but this is due to the extra \\ at the end of the eqnarray, which is now taken into account (... but not by dvipng apparently (*)); removing it (as shown in documented eqnarray examples, e.g. http://latexref.xyz/eqnarray.html, https://texfaq.org/FAQ-eqnarray) handles that.

(*) but hopefully we'll get rid of dvipng anyways in favor of directly rendering the glyphs ourselves; see e.g. #22459 (comment).

Edit: no, that's not enough if the last line has nonzero descent. Back to the drawing board.

PR Checklist

Tests and Styling

• Has pytest style unit tests (and pytest passes).
• Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

• New features are documented, with examples if plot related.
• New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
• API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
• Documentation is sphinx and numpydoc compliant (the docs should build without error).