Recommend not exposing OrPort for bridges

Enabling AssumeReachable 1 in torrc we can avoid publishing the OrPort in bridges. Are we ok recommending to do that to bridge operators?

If we decide to move forward with this those are the steps needed for it:

• Don't use the running flag in metrics ( tpo/network-health/team#318)
• update Docker images to don't expose OrPort
  • obfs4
  • webtunnel
• update documentation https://community.torproject.org/relay/setup/bridge/
• write an email to tor-relays@lists.torproject.org about it