Removed is_graded attribute. In HTML yaml it is not used, and that is not graded.

common/lib/xmodule/xmodule/templates/videoalpha/default.yaml

 ---
 metadata:
     display_name: Video Alpha 1
-    is_graded: False
     version: 1
 data: |
   <videoalpha show_captions="true" sub="name_of_file" youtube="0.75:JMD_ifUUfsU,1.0:OEoXaMPEzfM,1.25:AKqURZnYqpk,1.50:DYpADpL7jAY" >