Updates examples for video [(#968)](GoogleCloudPlatform/python-docs-samples#968)

Author: gguuss

samples/shotchange/README.rst

@@ -91,7 +91,7 @@ To run this sample:
     
     Example Usage:
     
-        python shotchange.py gs://cloudmleap/video/googlework.mp4
+        python shotchange.py gs://demomaker/gbikes_dinosaur.mp4
     
     positional arguments:
       path        GCS path for shot change detection.