refactor: procedure scope

Assets/Level01Controller.cs

@@ -20,7 +20,7 @@ public class Level01Controller : MonoBehaviour
         missionText.SetText(SetTextMission());
     }
 
-    string SetTextMission()
+    private string SetTextMission()
     {
         return $"Your Mission\nKill Keroco     {EnemyDeathCount}/{maxKerocoDeath}";
     }

Assets/Level02Controller.cs

@@ -27,7 +27,7 @@ public class Level02Controller : MonoBehaviour
         EventManager.StopListening("LeaderOfEnemyDeath", IncrementLeaderOfEnemyDeathCount);
     }
 
-    string SetTextMission()
+    private string SetTextMission()
     {
         return $"Your Mission\nKill Keroco     {EnemyDeathCount}/{maxKerocoDeath}\nKill Kepala Keroco   {EnemyLeaderDeathCount}/{maxLeaderOfKerocoDeath}";
     }

Assets/Level03Controller.cs

@@ -32,7 +32,7 @@ public class Level03Controller : MonoBehaviour
         EventManager.StopListening("AdmiralOfEnemyDeath", IncrementAdmiralOfEnemyDeathCount);
     }
     
-    string SetTextMission()
+    private string SetTextMission()
     {
         return $"Your Mission\nKill Kepala Keroco   {EnemyLeaderDeathCount}/{maxLeaderOfKerocoDeath}\nKill Jenderal     {EnemyAdmiralDeathCount}/{maxAdmiralOfKerocoDeath}";
     }

Assets/Level04Controller.cs

@@ -33,7 +33,7 @@ public class Level04Controller : MonoBehaviour
         EventManager.StopListening("KingOfEnemyDeath", IncrementKingOfEnemyDeathCount);
     }
 
-    string SetTextMission()
+    private string SetTextMission()
     {
         return $"Your Mission\nKill Kepala Keroco   {EnemyLeaderDeathCount}/{maxLeaderKerocoDeath}\nKill Jenderal     {EnemyAdmiralDeathCount}/{maxAdmiralOfKerocoDeath}\nKill King     {EnemyKingDeathCount}/{maxKingOfKerocoDeath}";
     }