Fix compiler error introduced by 5386bfb9c1.

Per buildfarm member wrasse, void function cannot return a value.
This only affects v13-v17, where an ABI-compatible wrapper function
was added.

Backpatch-through: 13-17

src/backend/executor/execMain.c

@@ -1186,7 +1186,7 @@ CheckValidResultRelNew(ResultRelInfo *resultRelInfo, CmdType operation,
 void
 CheckValidResultRel(ResultRelInfo *resultRelInfo, CmdType operation)
 {
-	return CheckValidResultRelNew(resultRelInfo, operation, ONCONFLICT_NONE, NIL);
+	CheckValidResultRelNew(resultRelInfo, operation, ONCONFLICT_NONE, NIL);
 }
 
 /*