Remove TODOs to remove the "new back shortcut bubble".

chrome/browser/ui/views/new_back_shortcut_bubble.h

Index: chrome/browser/ui/views/new_back_shortcut_bubble.h
diff --git a/chrome/browser/ui/views/new_back_shortcut_bubble.h b/chrome/browser/ui/views/new_back_shortcut_bubble.h
index 92eb074f9769ae1d252f68571c88f03ef40e9a45..88b2565bc036f678726c86fcc2393ff3bd44edc6 100644
--- a/chrome/browser/ui/views/new_back_shortcut_bubble.h
+++ b/chrome/browser/ui/views/new_back_shortcut_bubble.h
@@ -27,9 +27,8 @@ class Widget;
 
 // NewBackShortcutBubble shows a short-lived notification along the top of the
 // screen when the user presses the old Back/Forward shortcut, telling them how
-// to use the new shortcut. This will only be available for a few milestones to
-// let users adapt.
-// TODO(mgiuca): Remove this in M54 (https://crbug.com/610039).
+// to use the new shortcut. This notification only shows up the first few times
+// the user presses the old shortcut.
 class NewBackShortcutBubble : public gfx::AnimationDelegate {
  public:
   explicit NewBackShortcutBubble(ExclusiveAccessBubbleViewsContext* context);