doc: Update error messages in RLS examples

Since 8b9e9644d, the messages for failed permissions checks report
"table" where appropriate, rather than "relation".

Backpatch to all supported branches

doc/src/sgml/ddl.sgml

@@ -2569,7 +2569,7 @@ postgres=> table passwd;
 postgres=> set role alice;
 SET
 postgres=> table passwd;
-ERROR:  permission denied for relation passwd
+ERROR:  permission denied for table passwd
 postgres=> select user_name,real_name,home_phone,extra_info,home_dir,shell from passwd;
  user_name | real_name |  home_phone  | extra_info | home_dir    |   shell
 -----------+-----------+--------------+------------+-------------+-----------
@@ -2579,7 +2579,7 @@ postgres=> select user_name,real_name,home_phone,extra_info,home_dir,shell fr
 (3 rows)
 
 postgres=> update passwd set user_name = 'joe';
-ERROR:  permission denied for relation passwd
+ERROR:  permission denied for table passwd
 -- Alice is allowed to change her own real_name, but no others
 postgres=> update passwd set real_name = 'Alice Doe';
 UPDATE 1
@@ -2588,9 +2588,9 @@ UPDATE 0
 postgres=> update passwd set shell = '/bin/xx';
 ERROR:  new row violates WITH CHECK OPTION for "passwd"
 postgres=> delete from passwd;
-ERROR:  permission denied for relation passwd
+ERROR:  permission denied for table passwd
 postgres=> insert into passwd (user_name) values ('xxx');
-ERROR:  permission denied for relation passwd
+ERROR:  permission denied for table passwd
 -- Alice can change her own password; RLS silently prevents updating other rows
 postgres=> update passwd set pwhash = 'abc';
 UPDATE 1