Allow the zed app to connect to both the old and new rpc endpoints

In the case of the new Next.js app, the app will follow a redirect
from 'zed.dev/rpc' to the subdomain where the rust service is hosted.
Until then, the app will connect directly to zed.dev/rpc.

crates/client/src/channel.rs

@@ -599,8 +599,8 @@ mod tests {
     #[gpui::test]
     async fn test_channel_messages(mut cx: TestAppContext) {
         let user_id = 5;
-        let mut client = Client::new();
         let http_client = FakeHttpClient::new(|_| async move { Ok(Response::new(404)) });
+        let mut client = Client::new(http_client.clone());
         let server = FakeServer::for_client(user_id, &mut client, &cx).await;
         let user_store = cx.add_model(|cx| UserStore::new(client.clone(), http_client, cx));