recent projects: cleanup ui (#7528)

As the ui for the file finder was recently changed in #7364, I think it
makes sense to also update the ui of the recent projects overlay.

Before:

![image](https://github.com/zed-industries/zed/assets/53836821/8a0f5bef-9b37-40f3-a974-9dfd7833cc71)

After:

![image](https://github.com/zed-industries/zed/assets/53836821/7e9f934a-1ac3-4716-b7b6-67a7435f3bde)


Release Notes:

- Improved UI of recent project overlay

crates/collab_ui/src/collab_panel/channel_modal.rs

@@ -43,7 +43,7 @@ impl ChannelModal {
         cx.observe(&channel_store, |_, _, cx| cx.notify()).detach();
         let channel_modal = cx.view().downgrade();
         let picker = cx.new_view(|cx| {
-            Picker::new(
+            Picker::uniform_list(
                 ChannelModalDelegate {
                     channel_modal,
                     matching_users: Vec::new(),