Cleaned up sphinx docs utilities in gwpy.utils
This PR cleans up gwpy.utils.sphinx
by removing the following custom extensions:
-
gwpy.utils.sphinx.numpydoc
-numpydoc >= 0.8.0
is good enough -
gwpy.utils.sphinx.directives
- we don't need these -
gwpy.utils.sphinx.autoclassapi
- we haven't actually used this in a while