2018.4 CreatePrefab(string, UnityEngine.GameObject)' is obsolete: `Use SaveAsPrefabAsset instead

Fixed in next update.

PointCloud2MeshConverter.cs(1016,52): warning CS0618: `UnityEditor.PrefabUtility.CreatePrefab(string, UnityEngine.GameObject)' is obsolete: `Use SaveAsPrefabAsset instead.'

```
// old
#if UNITY_2019_1_OR_NEWER
```


```
// fixed
#if UNITY_2018_4_OR_NEWER

```