Updated edx video ID string

Subject to @nasthagiri 's review, please replace with:
After a file uploads successfully, automated processing can begin at edX. After automated processing begins for a file it is listed under Previous Uploads as In Progress. When the status is Complete, edX assigns a unique video ID to the video file and you can add it to your course. If something goes wrong, the Failed status message appears. Check for problems in the file and upload a replacement.