correct max step...

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

   agentParameters:
     maxStep: 0
   hasUpgradedFromAgentParameters: 1
-  MaxStep: 3000
+  MaxStep: 600
   ball: {fileID: 1273406647218856}
   invertX: 1
   score: 0