reduce time horizon tennis

config/trainer_config.yaml

     hidden_units: 512
     beta: 2.0e-2
     threaded: false
-    time_horizon: 1000
+    time_horizon: 50
+    normalize: true
-        window: 100
+        window: 10
         play_against_latest_model_ratio: 0.5
         save_steps: 50000
         swap_steps: 2000