Fix path to PushBlock demo (#5198)

(cherry picked from commit 875feb01509d8191fc3cc60d6a08c931546fb6dc)

config/imitation/PushBlock.yaml

         learning_rate: 0.0003
         use_actions: false
         use_vail: false
-        demo_path: Project/Assets/ML-Agents/Examples/PushBlock/Demos/ExpertPush.demo
+        demo_path: Project/Assets/ML-Agents/Examples/PushBlock/Demos/ExpertPushBlock.demo
-    max_steps: 1000000
+    max_steps: 100000
-      demo_path: Project/Assets/ML-Agents/Examples/PushBlock/Demos/ExpertPush.demo
+      demo_path: Project/Assets/ML-Agents/Examples/PushBlock/Demos/ExpertPushBlock.demo
       steps: 50000
       strength: 1.0
       samples_per_update: 0