Core/Scripts: Reverted part of 00f343af52, that is not a typo and fixed the hook properly

src/server/game/Scripting/ScriptMgr.cpp

@@ -422,7 +422,7 @@ void ScriptMgr::OnShutdownCancel()
 
 void ScriptMgr::OnWorldUpdate(uint32 diff)
 {
-    FOREACH_SCRIPT(WorldScript)->OnUpdate(NULL, diff);
+    FOREACH_SCRIPT(WorldScript)->OnUpdate(diff);
 }
 
 void ScriptMgr::OnHonorCalculation(float& honor, uint8 level, float multiplier)

src/server/game/Scripting/ScriptMgr.h

@@ -261,7 +261,7 @@ class WorldScript : public ScriptObject, public UpdatableScript<void>
         virtual void OnShutdownCancel() { }
 
         // Called on every world tick (don't execute too heavy code here).
-        virtual void OnWorldUpdate(uint32 /*diff*/) { }
+        virtual void OnUpdate(uint32 /*diff*/) { }
 
         // Called when the world is started.
         virtual void OnStartup() { }