Remove unused missed_update state (#25832)

app/javascript/mastodon/reducers/index.ts

@@ -26,7 +26,6 @@ import lists from './lists';
 import markers from './markers';
 import media_attachments from './media_attachments';
 import meta from './meta';
-import { missedUpdatesReducer } from './missed_updates';
 import { modalReducer } from './modal';
 import mutes from './mutes';
 import notifications from './notifications';
@@ -82,7 +81,6 @@ const reducers = {
   suggestions,
   polls,
   trends,
-  missed_updates: missedUpdatesReducer,
   markers,
   picture_in_picture,
   history,