Remove never-used client parameter from message handler functions (#13406)

Every single client-side RPC message handler function took an unused
`Arc<Client>` parameter. This removes that.

Release Notes:

- N/A

crates/dev_server_projects/src/dev_server_projects.rs

@@ -124,7 +124,6 @@ impl Store {
     async fn handle_dev_server_projects_update(
         this: Model<Self>,
         envelope: TypedEnvelope<proto::DevServerProjectsUpdate>,
-        _: Arc<Client>,
         mut cx: AsyncAppContext,
     ) -> Result<()> {
         this.update(&mut cx, |this, cx| {