[tor-project] meek-azure now using the cymru backend (Tor Browser 6.5.1 and 7.0a2)

With the recent releases of Tor Browser 6.5.1 and 7.0a2, Tor Browser users will now be using the new CDN backend and bridge when they select meek-azure. This will be a good time to monitor bridge usage and check if anything unexpected happens. If all goes well, we can queue up meek-amazon for the next release.