admin/doc-requirements: bump sphinx to 4.4.0

admin/doc-requirements: bump sphinx to 4.4.0

bump sphinx to latest stable. to address following build failure

ERROR: sphinx-autodoc-typehints 1.17.0 has requirement Sphinx>=4, but you'll have sphinx 3.5.4 which is incompatible.
ERROR: sphinx-substitution-extensions 2022.2.16 has requirement sphinx>=4.0.0, but you'll have sphinx 3.5.4 which is incompatible.

also bump bump sphinx-rtd-theme, otherwise we'd have following
build failure:

ERROR: sphinx-rtd-theme 0.5.2 has requirement docutils<0.17, but you'll have docutils 0.17.1 which is incompatible.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>