Shutdown embeds app

Shutdown embeds app (runs on apps-xx).

We disabled embeds in Gitter 19.15.0 via https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1223

• Cancel Transloadit subscription
  • We use transloadit for uploaded files and avatars
• Remove embeds completely from the frontend, https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1275
• Stop embeds on existing servers
  • https://gitlab.com/gitlab-com/gl-infra/gitter-infrastructure/merge_requests/79
  • https://gitlab.com/gitlab-com/gl-infra/gitter-infrastructure/merge_requests/86
• Remove server-side collapse endpoints, https://gitlab.com/gitlab-org/gitter/webapp/merge_requests/1276
• Remove embeds-deprecated feature flag

$ ssh mongo-replica-01.prod.gitter
$ mongo mongo-replica-01.prod.gitter
> use gitter
> db.featuretoggles.findOne({ name: "embeds-deprecated" })
{
        "_id" : ObjectId("5b6a68bdd73408ce4fa3df4a"),
        "name" : "embeds-deprecated",
        "__v" : 0,
        "description" : "This iteration of embeds is disabled by default because they are large and disruptive"
}
> db.featuretoggles.remove({ name: "embeds-deprecated" })