fix action size

Project/Assets/ML-Agents/Examples/3DBall/Prefabs/3DBall.prefab

     VectorObservationSize: 8
     NumStackedVectorObservations: 1
     m_ActionSpec:
-      m_NumContinuousActions: 0
-      BranchSizes: 0a0000000a000000
-    VectorActionSize: 0a0000000a000000
+      m_NumContinuousActions: 2
+      BranchSizes: 
+    VectorActionSize: 02000000
-    VectorActionSpaceType: 0
+    VectorActionSpaceType: 1
     hasUpgradedBrainParametersWithActionSpec: 1
   m_Model: {fileID: 5022602860645237092, guid: 35d5202e6dbc04a50934f20df199b47f, type: 3}
   m_InferenceDevice: 2