Remove CommandCounterIncrement() after processing ON COMMIT DELETE

This comes from f9b5b41e, which is part of one the original commits that
implemented ON COMMIT actions.  By looking at the truncation code, any
CCI needed happens locally when rebuilding indexes, so it looks safe to
just remove this final incrementation.

Author: Michael Paquier
Reviewed-by: Álvaro Herrera
Discussion: https://postgr.es/m/20181109024731.GF2652@paquier.xyz

src/backend/commands/tablecmds.c

@@ -13334,10 +13334,8 @@ PreCommit_on_commit_actions(void)
 	 * exists at truncation time.
 	 */
 	if (oids_to_truncate != NIL)
-	{
 		heap_truncate(oids_to_truncate);
-		CommandCounterIncrement();	/* XXX needed? */
-	}
+
 	if (oids_to_drop != NIL)
 	{
 		ObjectAddresses *targetObjects = new_object_addresses();