Scripts: fixed a warning

src/server/scripts/EasternKingdoms/ScarletMonastery/boss_bloodmage_thalnos.cpp

@@ -58,7 +58,7 @@ struct boss_bloodmage_thalnos : public BossAI
         _Reset();
     }
 
-    void JustEngagedWith(Unit* who) override
+    void JustEngagedWith(Unit* /*who*/) override
     {
         Talk(SAY_AGGRO);
         _JustEngagedWith();