Web client: update lists when post removed

[wmurphyrd]

Removing an avatar or deleting a post doesn't drop it from the list. Ideally we'd have the list dynamically updating based on socket events and this would take care of itself (see https://trello.com/c/voe8SQ0K/27-profile-pages-revamp), but for v4.0.0 maybe we just do some "optimistic UI" and delete them from the local memory so at least it's responsive to the change