update Tennis max step

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

   agentParameters:
     maxStep: 0
   hasUpgradedFromAgentParameters: 1
-  maxStep: 0
+  maxStep: 3000
   ball: {fileID: 1273406647218856}
   invertX: 0
   score: 0
+  timePenalty: 0
 --- !u!114 &2449890524009497851
 MonoBehaviour:
   m_ObjectHideFlags: 0
   m_Name: 
   m_EditorClassIdentifier: 
   areaObject: {fileID: 1541947554534326}
-  lastAgentHit: 0
-  lastFloorHit: 0
 --- !u!1 &1299636753784036
 GameObject:
   m_ObjectHideFlags: 0
   agentParameters:
     maxStep: 0
   hasUpgradedFromAgentParameters: 1
-  maxStep: 0
+  maxStep: 3000
   ball: {fileID: 1273406647218856}
   invertX: 1
   score: 0
+  timePenalty: 0
 --- !u!114 &6598495797138489682
 MonoBehaviour:
   m_ObjectHideFlags: 0

config/trainer_config.yaml

     time_horizon: 1000
     self_play:
         window: 10
-        play_against_latest_model_ratio: 0.2
+        play_against_latest_model_ratio: 0.5
         save_steps: 50000
         swap_steps: 50000
         team_change: 100000
     num_layers: 2
     self_play:
         window: 10
-        play_against_latest_model_ratio: 0.2
+        play_against_latest_model_ratio: 0.5
         save_steps: 50000
         swap_steps: 50000
         team_change: 200000