[pg15] fix: re-enable commented out GUC yb_plpgsql_disable_prefetch_i…

…n_for_query

Summary:
Fix TestPgReadCommittedFuncs test. This is done by changing QUERY_TUNING to QUERY_TUNING_METHOD.

Test Plan:
Jenkins: rebase: pg15

./yb_build.sh --java-test TestPgReadCommittedFuncs

Reviewers: pjain, jason, aagrawal, smishra

Reviewed By: jason

Subscribers: yql

Differential Revision: https://phorge.dev.yugabyte.com/D37496

src/postgres/src/backend/utils/misc/guc.c

@@ -2753,21 +2753,15 @@ static struct config_bool ConfigureNamesBool[] =
 		NULL, NULL, NULL
 	},
 
-#ifdef YB_TODO
-	/* deepthi@yugabyte
-	 * - QUERY_TUNING is no longer defined in Postgres source code.
-	 * - Please make appropriate modification.
-	 */
 	{
-		{"yb_plpgsql_disable_prefetch_in_for_query", PGC_USERSET, QUERY_TUNING,
+		{"yb_plpgsql_disable_prefetch_in_for_query", PGC_USERSET, QUERY_TUNING_METHOD,
 			gettext_noop("Disable prefetching in a PLPGSQL FOR loop over a query."),
 			NULL
 		},
 		&yb_plpgsql_disable_prefetch_in_for_query,
 		false,
 		NULL, NULL, NULL
 	},
-#endif
 
 	{
 		{"yb_enable_sequence_pushdown", PGC_USERSET, QUERY_TUNING_METHOD,