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_assistant.rs

@@ -204,7 +204,7 @@ impl InlineAssistant {
 
     pub fn inline_assist(
         workspace: &mut Workspace,
-        _action: &zed_actions::InlineAssist,
+        _action: &zed_actions::assistant::InlineAssist,
         cx: &mut ViewContext<Workspace>,
     ) {
         let settings = AssistantSettings::get_global(cx);