Refs #31233 -- Changed DatabaseWrapper._nodb_connection to _nodb_cursor().

It is now a method instead of a property and returns a context manager
that yields a cursor on entry and closes the cursor and connection upon
exit.

tests/postgres_tests/test_signals.py

@@ -38,4 +38,5 @@ class OIDTests(PostgreSQLTestCase):
 
     def test_register_type_handlers_no_db(self):
         """Registering type handlers for the nodb connection does nothing."""
-        register_type_handlers(connection._nodb_connection)
+        with connection._nodb_cursor() as cursor:
+            register_type_handlers(cursor.db)