Fix onion links for downloading Tor Browser

When using the onion service of torproject.org, clicking download links unfortunately redirects to clearnet dist.torproject.org instead of its onion service.

For example:

http://expyuzz4wqqyqhjn.onion/dist/torbrowser/6.5.2/torbrowser-install-6.5.2_en-US.exe

redirects to

https://dist.torproject.org/torbrowser/6.5.2/torbrowser-install-6.5.2_en-US.exe

instead of

http://rqef5a5mebgq46y5.onion/torbrowser/6.5.2/torbrowser-install-6.5.2_en-US.exe