Core/Spell: killed deprecated code which randomly changed powercost for missed spells

Added in 80d3cd43f6

Closes #5954

(cherry picked from commit b1072faa50493e287b5353056753d65ddcc445f3)

src/server/game/Spells/Spell.cpp

@@ -4761,10 +4761,7 @@ void Spell::TakePower()
             continue;
         }
 
-        if (hit)
-            m_caster->ModifyPower(powerType, -cost.Amount);
-        else
-            m_caster->ModifyPower(powerType, -irand(0, cost.Amount / 4));
+        m_caster->ModifyPower(powerType, -cost.Amount);
     }
 }