terminal: Fix context menu keybindings flicker (#15771)

Fixes https://github.com/zed-industries/zed/issues/15156


[Screencast_20240804_112659.webm](https://github.com/user-attachments/assets/d6d15e65-ece2-4342-b2ca-55e3737a4736)

Release Notes:

- N/A

crates/terminal_view/src/terminal_view.rs

@@ -211,7 +211,8 @@ impl TerminalView {
         cx: &mut ViewContext<Self>,
     ) {
         let context_menu = ContextMenu::build(cx, |menu, _| {
-            menu.action("New Terminal", Box::new(NewTerminal))
+            menu.context(self.focus_handle.clone())
+                .action("New Terminal", Box::new(NewTerminal))
                 .separator()
                 .action("Copy", Box::new(Copy))
                 .action("Paste", Box::new(Paste))