collab_ui: remove branch menu popover in favor of opening a modal (#12562)

This commit also removes a bunch of dead code.

Fixes #12544

Release Notes:

- Removed branch popover menu - clicking on the branch name in left-hand
corner now always opens a branch modal

crates/recent_projects/src/recent_projects.rs

@@ -118,16 +118,6 @@ impl RecentProjects {
             modal
         })
     }
-
-    pub fn open_popover(workspace: WeakView<Workspace>, cx: &mut WindowContext<'_>) -> View<Self> {
-        cx.new_view(|cx| {
-            Self::new(
-                RecentProjectsDelegate::new(workspace, false, false),
-                20.,
-                cx,
-            )
-        })
-    }
 }
 
 impl EventEmitter<DismissEvent> for RecentProjects {}