Fixing crash when Editor Application is quitting in Runtime Mode

Dispose was not called when editor was quitting resulting in a crash in the Job system when CPU Workers were disposed in finalizers by the garbage collector on the wrong thread.

Author: Codengineer

com.unity.ml-agents/Runtime/Academy.cs

@@ -261,6 +261,7 @@ protected Academy()
             LazyInitialize();
 
 #if UNITY_EDITOR
+            EditorApplication.quitting += Dispose;
             EditorApplication.playModeStateChanged += HandleOnPlayModeChanged;
 #endif
         }