Fix typos in comment and log message.

Author: MasaoFujii

src/backend/catalog/aclchk.c

@@ -5104,7 +5104,7 @@ pg_publication_ownercheck(Oid pub_oid, Oid roleid)
 }
 
 /*
- * Ownership check for an subscription (specified by OID).
+ * Ownership check for a subscription (specified by OID).
  */
 bool
 pg_subscription_ownercheck(Oid sub_oid, Oid roleid)

src/backend/commands/subscriptioncmds.c

@@ -912,7 +912,7 @@ AlterSubscriptionOwner_internal(Relation rel, HeapTuple tup, Oid newOwnerId)
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 		  errmsg("permission denied to change owner of subscription \"%s\"",
 				 NameStr(form->subname)),
-			 errhint("The owner of an subscription must be a superuser.")));
+			 errhint("The owner of a subscription must be a superuser.")));
 
 	form->subowner = newOwnerId;
 	CatalogTupleUpdate(rel, &tup->t_self, tup);

src/test/regress/expected/subscription.out

@@ -105,7 +105,7 @@ ALTER SUBSCRIPTION testsub_foo RENAME TO testsub;
 -- fail - new owner must be superuser
 ALTER SUBSCRIPTION testsub OWNER TO regress_subscription_user2;
 ERROR:  permission denied to change owner of subscription "testsub"
-HINT:  The owner of an subscription must be a superuser.
+HINT:  The owner of a subscription must be a superuser.
 ALTER ROLE regress_subscription_user2 SUPERUSER;
 -- now it works
 ALTER SUBSCRIPTION testsub OWNER TO regress_subscription_user2;