Fix copy-paste error in errhint() introduced in 691d79a0.

Reported-By: Petr Jelinek
Discussion: https://postgr.es/m/c95a620b-34f0-7930-aeb5-f7ab804f26cb@2ndquadrant.com
Backpatch: 9.4-, like the previous commit

src/backend/replication/slot.c

@@ -1524,7 +1524,7 @@ RestoreSlotFromDisk(const char *name)
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("logical replication slot \"%s\" exists, but wal_level < logical",
 						NameStr(cp.slotdata.name)),
-				 errhint("Change wal_level to be replica or higher.")));
+				 errhint("Change wal_level to be logical or higher.")));
 	else if (wal_level < WAL_LEVEL_REPLICA)
 		ereport(FATAL,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),