fix: Add html-validate suppression that should have been part of #6356 (#6440)

ietf/templates/group/all_photos.html

@@ -8,6 +8,7 @@
     <h1>{{ group_type | upper }} {{ role }} photos</h1>
     {% regroup roles|dictsort:"last_initial" by last_initial as alphabet_blocks %}
     {% for letter in alphabet_blocks %}
+        <!-- [html-validate-disable-next valid-id -- Unicode IDs are OK in HTML5] -->
         <h2 class="mt-4" {% if letter.grouper|slugify %}id="{{ letter.grouper }}"{% endif %}>{{ letter.grouper }}</h2>
         {% regroup letter.list by person as person_groups %}
         {# keep in sync with group_photos.html #}