update comment in test

Author: rjduffner

instrumentation/opentelemetry-instrumentation-psycopg2/tests/test_psycopg2_instrumentation.py

@@ -95,9 +95,8 @@ def test_instrumentation_dependencies_both_installed(
         instrumentation = Psycopg2Instrumentor()
 
         def _distribution(name):
-            # Function raises PackageNotFoundError
-            # if name is not in the list. We will
-            # not raise it for both names
+            # The function returns None here for all names
+            # to simulate both packages being installed
             return None
 
         mock_distribution.side_effect = _distribution