Fix disabled all_results button, overriding arclight view _group_toggle

[rshiggin]

Override Arclight view with UM custom version. Adds ?group=false || ?group=true to URL query when user toggles "All results" and "Grouped by collection" on search_results page.

Default remains "Grouped . . . "

 <div class="result-type-group btn-group" role="group" aria-label="<%= t('arclight.views.index.group_results') %>">
   <%= link_to t('arclight.views.index.all_results'),
-              search_catalog_path(search_without_group),
+              search_catalog_path(search_without_group.merge('group' => 'false')),
               class: "btn btn-outline-secondary #{'active' unless grouped?}"
   %>
   <%= link_to t('arclight.views.index.group_by_collection'),

The "All results" link previously removed "group" entirely. Adding group=false makes the user’s choice survive the defaulting logic.