[Port] [6000.4] Fix mppm asset database readonly by setting vfxmanager dirty

Author: svc-reach-platform-support

Packages/com.unity.visualeffectgraph/Editor/Models/VFXGraph.cs

@@ -214,6 +214,8 @@ static void CheckCompilationVersion()
                 compiledVersionProperty.intValue = (int)VFXGraphCompiledData.compiledVersion;
                 runtimeVersionProperty.intValue = (int)VisualEffectAsset.currentRuntimeDataVersion;
                 serializedVFXManager.ApplyModifiedProperties();
+                EditorUtility.SetDirty(vfxmanager);
+                AssetDatabase.SaveAssets();
 
                 AssetDatabase.StartAssetEditing();
                 try