Consolidate Assistant panels in assistant2 feature flag (#23442)

This PR consolidates the two Assistant panels into one for users in the
`assistant2` feature flag.

Now that the Assistant1 prompt editor is accessible through the
Assistant2 panel, we no longer have a need to show both panels.

Release Notes:

- N/A

crates/assistant2/src/inline_prompt_editor.rs

@@ -270,9 +270,10 @@ impl<T: 'static> PromptEditor<T> {
             PromptEditorMode::Terminal { .. } => "Generate",
         };
 
-        let assistant_panel_keybinding = ui::text_for_action(&crate::ToggleFocus, cx)
-            .map(|keybinding| format!("{keybinding} to chat ― "))
-            .unwrap_or_default();
+        let assistant_panel_keybinding =
+            ui::text_for_action(&zed_actions::assistant::ToggleFocus, cx)
+                .map(|keybinding| format!("{keybinding} to chat ― "))
+                .unwrap_or_default();
 
         format!("{action}… ({assistant_panel_keybinding}↓↑ for history)")
     }