Fix avatars animating in chat list when going back from a conversation.

This was caused by OWSViewController's behavior of automatic tracking of the
keyboard frame, which caused ChatListVC.view.layoutSubviews() being called
within an animation block while navigation pop.

Disable keyboard frame tracking for ChatListVC because we don't use keyboard
metrics in that view.

Signal/src/ViewControllers/HomeView/Chat List/ChatListViewController.swift

@@ -27,6 +27,8 @@ public class ChatListViewController: OWSViewController {
     public override func viewDidLoad() {
         super.viewDidLoad()
 
+        keyboardObservationBehavior = .never
+
         switch chatListMode {
         case .inbox:
             title = NSLocalizedString("CHAT_LIST_TITLE_INBOX", comment: "Title for the chat list's default mode.")