Updated edx video ID string

@nasthagiri : This description ("Monitoring files as they upload") is only meant to cover the statuses and thermometer that display in the tiles as the files are transferred to the edX servers. The description under the next heading ("Managing uploaded files") is meant to give cues as to what happens at edX, and how you know whether it's done. 
- If the *upload* fails, what should course teams do, other than try uploading the file again? Why would the upload fail? 
- If the VEDA process fails, course teams should make sure that the file that they sent isn't corrupt. Whether it was corrupted on their end or not, they should upload again, right? Although if the file on their end is not corrupt, they should make sure that they comply with all specifications for success, and then upload again when they have a file that does meet those standards. I will rewrite the last sentence in line 255.