Customize "Proxy server is refusing connections" error messages in Tor Browser

Design from network_connection:

While testing the paper prototype, we felt the need for this screen to autorefresh to detect automatically when Tor is started. This might be a side-effect of the paper prototype. Other such screens in Firefox don't autorefresh. We might wait until we test the software beta before implementing the autorefresh.

• Remove the doc introduced in e5492095.