Remove useless if-test.

Coverity complained that this check is pointless, and it's right.
There is no case where we'd call ExecutorStart with a null plannedstmt,
and if we did, it'd have crashed before here.  Thinko in commit cc415a56.

src/backend/executor/execMain.c

@@ -249,9 +249,7 @@ standard_ExecutorStart(QueryDesc *queryDesc, int eflags)
 	estate->es_crosscheck_snapshot = RegisterSnapshot(queryDesc->crosscheck_snapshot);
 	estate->es_top_eflags = eflags;
 	estate->es_instrument = queryDesc->instrument_options;
-
-	if (queryDesc->plannedstmt)
-		estate->es_jit_flags = queryDesc->plannedstmt->jitFlags;
+	estate->es_jit_flags = queryDesc->plannedstmt->jitFlags;
 
 	/*
 	 * Set up an AFTER-trigger statement context, unless told not to, or