Hide chat panel button when not in a call (#22200)

cc @nathansobo 

Release Notes:

- Hide chat panel button by default when not in a call

crates/collab_ui/src/collab_ui.rs

@@ -14,7 +14,7 @@ use gpui::{
 };
 use panel_settings::MessageEditorSettings;
 pub use panel_settings::{
-    ChatPanelSettings, CollaborationPanelSettings, NotificationPanelSettings,
+    ChatPanelButton, ChatPanelSettings, CollaborationPanelSettings, NotificationPanelSettings,
 };
 use release_channel::ReleaseChannel;
 use settings::Settings;