Change the hashtag column to not display the hashtag header on pinned columns (#26416)

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

@@ -203,7 +203,7 @@ class HashtagTimeline extends PureComponent {
         </ColumnHeader>
 
         <StatusListContainer
-          prepend={<HashtagHeader tag={tag} disabled={!signedIn} onClick={this.handleFollow} />}
+          prepend={pinned ? null : <HashtagHeader tag={tag} disabled={!signedIn} onClick={this.handleFollow} />}
           alwaysPrepend
           trackScroll={!pinned}
           scrollKey={`hashtag_timeline-${columnId}`}