Changes to model don't invalidate Sphinx cache

If a Pydantic field is modified and the rST remains unchanged, you must run `make clean` before `make docs`. Otherwise, Sphinx will not rebuild the document, as the reStructuredText has not changed.

This behavior diverges from autodoc, which renders changes to docstrings regardless of whether the rST has been modified or not.

This change would make iterating on kitbash documents locally much easier and less cumbersome.