DB/Gameobject: Fix faction of door before Kel'Thuzad, making it untargetable.

Players should now be unable to reach Kel'Thuzad before killing Sapphiron.

sql/updates/world/2011_05_30_05_world_gameobject_template.sql

@@ -0,0 +1,2 @@
+-- Fix faction for Frostwyrm Waterfall Door (door after Sapphiron in Naxxramas)
+UPDATE `gameobject_template` SET `faction`=1375 WHERE `entry`=181225;