Dropbox files are not supported in Hubs Cloud, but work on HMC

Background:
Prior to https://github.com/mozilla/reticulum/pull/370 it was possible to stream video files from Dropbox by replacing the `?dl=0` query parameter in the 'Share' URL for Dropbox files with `?raw=1`. 370 removed that requirement by auto-handling the URL and swapping it so the link that was generated by the 'Share' dialogue would auto-magically work.

However, in Hubs Cloud deployments, neither option for Dropbox URLs work. The media throws a 'Not Found' error for files that otherwise work on hubs.mozilla.com.

Test URL (from Share menu): https://www.dropbox.com/s/j6l59aphmzqsfq0/livs%20potg%20amazing%20push.mp4?dl=0

Test URL (raw download): https://www.dropbox.com/s/j6l59aphmzqsfq0/livs%20potg%20amazing%20push.mp4?raw=1

**Expected**: Works in Hubs Cloud and hubs.mozilla.com
**Actual**: Only works on hubs.mozilla.com

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/HUBS-1050)

Start by reviewing the Dropbox URL handling described in reticulum pull request 370 and reproduce the issue with the two Dropbox URLs in this report. Compare media behavior in Hubs Cloud with hubs.mozilla.com, then verify that both the Share URL and raw-download URL work in Hubs Cloud as well.

Written by the indexing model from the issue text.