gh-36744: pep8 for maxima-lib interface
Just a full pep8 cleanup of the modified file.
### :memo: Checklist
- [x] The title is concise, informative, and self-explanatory.
- [x] The description explains in detail what this PR is about.
URL: https://github.com/sagemath/sage/pull/36744
Reported by: Frédéric Chapoton
Reviewer(s): Travis Scrimshaw
