fix: build fail because of editor using

Author: Renardjojo

Runtime/IInfluencer.cs

@@ -1,5 +1,3 @@
-using System.Collections;
-using System.Collections.Generic;
 using UnityEngine;
 
 namespace InfluenceMapPackage

Runtime/TerrainInfluenceMap.cs

@@ -1,12 +1,13 @@
-using System;
 using System.Collections.Generic;
 using Unity.Profiling;
-using UnityEditor;
-using UnityEditor.VersionControl;
 using UnityEngine;
 using UnityEngine.Assertions;
 using UnityEngine.Rendering;
 
+#if UNITY_EDITOR
+using UnityEditor;
+#endif
+
 namespace InfluenceMapPackage
 {
     [RequireComponent(typeof(Terrain))]