Fixing entrypoint bug

With the release of importlib_metadata 5.0 deprecation of an endpoint
has caused stevedore to fail (at least in python 3.7).  For now, I'm
pinning importlib-metadata to < 5.0.

See:
* python/importlib_metadata#409
* https://stackoverflow.com/questions/73929564/entrypoints-object-has-no-attribute-get-digital-ocean

setup.py

@@ -31,6 +31,7 @@
         "dnspython",  # Needed to be able to connect using domain name rather than IP
         "pymongo<4.0",
         "litemongo",
+        "importlib-metadata<5.0",  # see: https://stackoverflow.com/questions/73929564/entrypoints-object-has-no-attribute-get-digital-ocean
         "mongomock",
         "bidict",
         "networkx",  # For reference graphs