Bluesky: interpret logged-in visibility on bsky.app as opt-out

[snarfed]

The official bsky.app client lets you configure it to only show your profile to logged in users. We should interpret this as opting out of Bridgy Fed too. Here's an example of the label on a app.bsky.actor.profile:

   "labels" : [
      {
         "cid" : "bafyreigsv3xvt7c6agnfis74gq3vbxnipbvx4u65etg4xdy3ewvrwybioi",
         "cts" : "1970-01-01T00:00:00.000Z",
         "neg" : false,
         "src" : "did:plc:2wyqv44lm72vasmddeqjgy72",
         "uri" : "at://did:plc:2wyqv44lm72vasmddeqjgy72/app.bsky.actor.profile/self",
         "val" : "!no-unauthenticated"
      }
   ],