ssh remoting: Show the host's GitHub name in the titlebar when sharing an SSH project (#19844)

The name (GitHub name) of the host was not displayed when sharing an ssh
project.

Previously we assumed that the a collaborator is a host if the
`replica_id` of the collaborator was `0`,
but for ssh project the `replica_id` is actually `1`.

<img width="329" alt="Screenshot 2024-10-28 at 18 16 30"
src="https://github.com/user-attachments/assets/c0151e12-a96f-4f38-aec1-4ed5475a9eaf">


Co-Authored-by: Thorsten <thorsten@zed.dev>

Release Notes:

- N/A

---------

Co-authored-by: Thorsten <thorsten@zed.dev>

crates/collab/src/db/tests/buffer_tests.rs

@@ -121,11 +121,13 @@ async fn test_channel_buffers(db: &Arc<Database>) {
                 user_id: a_id.to_proto(),
                 peer_id: Some(rpc::proto::PeerId { id: 1, owner_id }),
                 replica_id: 0,
+                is_host: false,
             },
             rpc::proto::Collaborator {
                 user_id: b_id.to_proto(),
                 peer_id: Some(rpc::proto::PeerId { id: 2, owner_id }),
                 replica_id: 1,
+                is_host: false,
             }
         ]
     );