Don't limit use of importlib-metadata to Python < 3.8
The cinder requirements job is failing because our restriction
of importlib_metadata to py<3.8 is conflicting with change
to global-requirements.
The cinder restriction to py<3.8 was originally made by
change (merged 21 Aug 2020).
@@ -7,7 +7,7 @@ decorator>=4.4.2 # BSD
eventlet>=0.30.1,!=0.32.0 # MIT
greenlet>=0.4.16 # MIT
httplib2>=0.18.1 # MIT
-importlib_metadata>=3.1.1;python_version<'3.8' # Apache-2.0
+importlib_metadata>=3.1.1 # Apache-2.0
iso8601>=0.1.12 # MIT
jsonschema>=3.2.0 # MIT
keystoneauth1>=4.2.1 # Apache-2.0
