agent: Remove unused agent: chat mode command palette action (#29741)

We weren't using this one anymore. We used to use it for the switch that
toggled tools on, which doesn't exist anymore.

Release Notes:

- N/A

---------

Co-authored-by: Joseph T. Lyons <josephtlyons@gmail.com>

crates/agent/src/message_editor.rs

@@ -42,7 +42,7 @@ use crate::profile_selector::ProfileSelector;
 use crate::thread::{Thread, TokenUsageRatio};
 use crate::thread_store::ThreadStore;
 use crate::{
-    AgentDiff, Chat, ChatMode, ExpandMessageEditor, NewThread, OpenAgentDiff, RemoveAllContext,
+    AgentDiff, Chat, ExpandMessageEditor, NewThread, OpenAgentDiff, RemoveAllContext,
     ToggleContextPicker, ToggleProfileSelector,
 };
 
@@ -206,10 +206,6 @@ impl MessageEditor {
         &self.context_store
     }
 
-    fn toggle_chat_mode(&mut self, _: &ChatMode, _window: &mut Window, cx: &mut Context<Self>) {
-        cx.notify();
-    }
-
     pub fn expand_message_editor(
         &mut self,
         _: &ExpandMessageEditor,
@@ -499,7 +495,6 @@ impl MessageEditor {
             .on_action(cx.listener(Self::toggle_context_picker))
             .on_action(cx.listener(Self::remove_all_context))
             .on_action(cx.listener(Self::move_up))
-            .on_action(cx.listener(Self::toggle_chat_mode))
             .on_action(cx.listener(Self::expand_message_editor))
             .capture_action(cx.listener(Self::paste))
             .gap_2()