Unread indicator was invisible behind column header, adjusted (#3720)

* Unread indicator was invisible behind column header, adjusted

* Unread indicator now a CSS pseudo-element

* Adjust flex

app/javascript/mastodon/features/ui/containers/status_list_container.js

@@ -42,7 +42,6 @@ const makeMapStateToProps = () => {
   const mapStateToProps = (state, { timelineId }) => ({
     statusIds: getStatusIds(state, { type: timelineId }),
     isLoading: state.getIn(['timelines', timelineId, 'isLoading'], true),
-    isUnread: state.getIn(['timelines', timelineId, 'unread']) > 0,
     hasMore: !!state.getIn(['timelines', timelineId, 'next']),
   });