account for add_all optimisations in sqlalchemy 1.4

Author: mnbbrown

tests/opentelemetry-docker-tests/tests/sqlalchemy_tests/mixins.py

@@ -243,4 +243,4 @@ def insert_players(session):
                 close_all_sessions()
 
         spans = self.memory_exporter.get_finished_spans()
-        self.assertEqual(len(spans), 5)
+        self.assertEqual(len(spans), 5 if self.VENDOR not in ["postgresql"] else 3)