Revert "ui: problem_list: fix line break"

This reverts commit 7b48be5.

Author: cubercsl

webapp/templates/partials/problem_list.html.twig

@@ -94,7 +94,7 @@
                                                                 data-bs-toggle="tooltip"
                                                                 data-placement="top"
                                                                 data-html="true"
-                                                                title="Between {{ stat.start.timestamp | printtime(null, contest) }} and {{ stat.end.timestamp | printtime(null, contest) }}:{{ '\n' }}{{ label }}">
+                                                                title="Between {{ stat.start.timestamp | printtime(null, contest) }} and {{ stat.end.timestamp | printtime(null, contest) }}:<br/>{{ label }}">
                                                             </div>
                                                         {% endfor %}
                                                     </div>