agent_ui: Remove ellipses from some menu entries (#40858)

<img width="335" height="236" alt="image"
src="https://github.com/user-attachments/assets/5e09e9ed-f0f3-48df-ac22-032edfc6c114"
/>

Release Notes:
This PR fixes inconsistent use of trailing ellipsis (…) in the MCP
Server menu.
Previously, some menu items (like Add Custom Server…) used hardcoded
ellipses even though they didn’t trigger additional dialogs or steps.
This change removes unnecessary ellipses to align with standard UI/UX
conventions used across Zed’s menus.

---------

Co-authored-by: Danilo Leal <67129314+danilo-leal@users.noreply.github.com>

crates/agent_ui/src/agent_panel.rs

@@ -1663,7 +1663,7 @@ impl AgentPanel {
                             .separator();
 
                         menu = menu
-                            .action("Rules…", Box::new(OpenRulesLibrary::default()))
+                            .action("Rules", Box::new(OpenRulesLibrary::default()))
                             .action("Settings", Box::new(OpenSettings))
                             .separator()
                             .action(full_screen_label, Box::new(ToggleZoom));