Remove autoplay for video in course about page

The iframe was generated with autoplay=1, which, sometimes, would cause
the video to play in the background.

cms/djangoapps/models/settings/course_details.py

@@ -182,7 +182,7 @@ class CourseDetails(object):
         result = None
         if video_key:
             result = '<iframe width="560" height="315" src="//www.youtube.com/embed/' + \
-                video_key + '?autoplay=1&rel=0" frameborder="0" allowfullscreen=""></iframe>'
+                video_key + '?rel=0" frameborder="0" allowfullscreen=""></iframe>'
         return result