fix prefab

Project/Assets/ML-Agents/Examples/Tennis/Prefabs/TennisArea.prefab

   m_Name: 
   m_EditorClassIdentifier: 
   m_BrainParameters:
-    vectorObservationSize: 14
+    vectorObservationSize: 12
     numStackedVectorObservations: 3
     vectorActionSize: 03000000
     vectorActionDescriptions: []

Project/Assets/ML-Agents/Examples/Tennis/Scripts/TennisArea.cs

 
     public void MatchReset()
     {
-        var ballOut = Random.Range(12f, 14f);
+        var ballOut = Random.Range(12.5f, 14f);
         var flip = Random.Range(0, 2);
         if (flip == 0)
         {