Add back accidentally removed create_session in utils/db.py (#31705)

The create_session function was accidentally removed in commit
522661b
and it's a breaking change.

airflow/utils/db.py

@@ -40,7 +40,7 @@
 from airflow.utils import helpers
 
 # TODO: remove create_session once we decide to break backward compatibility
-from airflow.utils.session import NEW_SESSION, provide_session
+from airflow.utils.session import NEW_SESSION, create_session, provide_session  # noqa: F401
 
 if TYPE_CHECKING:
     from alembic.runtime.environment import EnvironmentContext

tests/utils/test_db.py

@@ -42,6 +42,9 @@
     compare_server_default,
     compare_type,
     create_default_connections,
+    # The create_session is not used. It is imported here to
+    # guard against removing it from utils.db accidentally
+    create_session,  # noqa: F401
     downgrade,
     resetdb,
     upgradedb,