Adjust some of the dependencies.
multi_key_dict is not shipped by OpenStack Zuul templates
`build-openstack-docs-pti` or `openstack-cover-jobs` we thus need to
depend on `requirements.txt`.
setuptools v66.0.0 removed support for PEP 440 non-conforming versions.
It provides pkg_resources which we use in PluginVersion.
Tox `whitelist_externals` has been renamed `allowlist_externals`.
Signed-off-by: Antoine Musso <hashar@free.fr>
Change-Id: Ie791c2bb0e7b3784913f45768d2f3db4c66ccae5