DB/Commands: Fix 2 commands permisions

Closes #13592

sql/updates/world/2014_11_19_00_world.sql

@@ -0,0 +1,6 @@
+--
+DELETE FROM `command` WHERE `name`='pvpstats';
+INSERT INTO `command` (`name`, `permission`, `help`) VALUES
+('pvpstats', 797, 'Shows number of battleground victories in the last 7 days');
+
+UPDATE `command` SET `permission`=798 WHERE `name`='modify xp';