pin importlib for earlier versions of python

Author: stephenc-pace

setup.py

@@ -30,9 +30,7 @@
         "opentelemetry-api",
         "opentelemetry-instrumentation",
         "opentelemetry-instrumentation-wsgi",
-        "importlib-metadata<=4.13.0",  # Temporary pin,
-        # remove when https://github.com/celery/kombu/pull/1601
-        # is in the most recent version of kombu
+        "importlib-metadata<5 ; python_version<='3.7'",
     ],
     extras_require={
         "dev": list(PACKAGE_INFO["_instruments"])