Update root post update at on reply delete (#28688)

* Update root post update at on reply delete

* Address feedback

server/channels/store/sqlstore/post_store.go

@@ -951,6 +951,13 @@ func (s *SqlPostStore) Delete(rctx request.CTX, postID string, time int64, delet
 		err = s.deleteThread(transaction, postID, time)
 	} else {
 		err = s.updateThreadAfterReplyDeletion(transaction, id.RootId, id.UserId)
+		updatePostQuery := s.getQueryBuilder().
+			Update("Posts").
+			Set("UpdateAt", time).
+			Where(sq.Eq{"Id": id.RootId})
+		if _, err = transaction.ExecBuilder(updatePostQuery); err != nil {
+			mlog.Warn("Error updating Post UpdateAt.", mlog.Err(err))
+		}
 	}
 
 	if err != nil {