Swap sr-only class for visuallyhidden, as sr-only is from bakerydemo css

wagtail/admin/templates/wagtailadmin/edit_handlers/tabbed_interface.html

@@ -21,7 +21,7 @@
                     </label>
 
                     <button class="comment-notifications-toggle-button" type="button">
-                        <span class="sr-only">{% trans "Toggle visibility of comment notifications dropdown" %}</span>
+                        <span class="visuallyhidden">{% trans "Toggle visibility of comment notifications dropdown" %}</span>
                         {% icon name="chevron-down" class_name="comment-notifications-toggle-button__icon" %}
                     </button>