Fixes streaming callbacks of HashtagTimeline (#3849)

app/javascript/mastodon/features/hashtag_timeline/index.js

@@ -60,7 +60,7 @@ class HashtagTimeline extends React.PureComponent {
       received (data) {
         switch(data.event) {
         case 'update':
-          dispatch(updateTimeline('tag', JSON.parse(data.payload)));
+          dispatch(updateTimeline(`hashtag:${id}`, JSON.parse(data.payload)));
           break;
         case 'delete':
           dispatch(deleteFromTimelines(data.payload));