This updates zuul-sphinx to retrieve version info from package metadata
using importlib.metadata instead of the now removed pkg_resources
library. This is necessary to run doc builds on top of python3.12 which
removed setuptools and pkg_resources by default.
An altnerative would be to explicitly require setuptools as a dependency
but stdlib importlib should be sufficient so we don't bother.
Change-Id: I5d73e7cc728188e7978e30eb5eb53d73e74b9ce2