Merged requested to merge enh/ci_sphinx into master
This MR bumps Sphinx version from unreleased branch
4.x and replaces
numpydoc extension with
This is connected with !386 development, but I decided to make it a separate MR, since it alters Docker images that are global for all branches.
The reason to replace current Sphinx with git version is that on current stable (4.0.2) only properties are documented in "Attributes" rubric:
while on unreleased 4.1 attributes are also captured correctly: