Fix thinko in comments.

A slot can not be stored in a tuple but it's vice versa.

Reported-by: Ashutosh Bapat
Author: Ashutosh Bapat
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/CAFjFpRcHhNhXdegyJv3KKDWrwO1_NB_KYZM_ZSDeMOZaL1A5jQ@mail.gmail.com

src/backend/executor/execReplication.c

@@ -417,7 +417,7 @@ ExecSimpleRelationInsert(EState *estate, TupleTableSlot *slot)
 		if (resultRelInfo->ri_PartitionCheck)
 			ExecPartitionCheck(resultRelInfo, slot, estate, true);
 
-		/* Store the slot into tuple that we can inspect. */
+		/* Materialize slot into a tuple that we can scribble upon. */
 		tuple = ExecMaterializeSlot(slot);
 
 		/* OK, store the tuple and create index entries for it */
@@ -484,7 +484,7 @@ ExecSimpleRelationUpdate(EState *estate, EPQState *epqstate,
 		if (resultRelInfo->ri_PartitionCheck)
 			ExecPartitionCheck(resultRelInfo, slot, estate, true);
 
-		/* Store the slot into tuple that we can write. */
+		/* Materialize slot into a tuple that we can scribble upon. */
 		tuple = ExecMaterializeSlot(slot);
 
 		/* OK, update the tuple and index entries for it */