[bug] Nested `apidoc_excluded_paths` default `[[str]]` causes a warning in Sphinx 8.2.0

[webknjaz]

Running Sphinx v8.2.0
loading translations [en]... done
WARNING: while setting up extension sphinxcontrib.apidoc: Failed to convert [[<class 'str'>]] to a frozenset
making output directory... done

(https://readthedocs.org/projects/awx-plugins-core/builds/27249215/)

[webknjaz]

@stephenfin let me know if you'd like any help with this and #22.

[webknjaz]

There's now a built-in extension with similar logic over in the upstream project: sphinx-doc/sphinx#13333. Perhaps, this one should just get deprecated and Sphinx 8.2+ users would migrate to the built-in solution.