Followup to #29310, #33104

We could consider to extend make doc-clean so that it also removes inventory, doctrees.
This should suffice to resolve incremental docbuild problems.

CC: @jhpalmieri @kwankyu

Component: build

Author: John Palmieri

Branch/Commit: 8244126

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/33705