Replace more font-awesome icons in views/admin area (#30961)

app/views/admin/settings/appearance/show.html.haml

@@ -33,7 +33,7 @@
       - if @admin_settings.mascot.persisted?
         = image_tag @admin_settings.mascot.file.url, class: 'fields-group__thumbnail'
         = link_to admin_site_upload_path(@admin_settings.mascot), data: { method: :delete }, class: 'link-button link-button--destructive' do
-          = fa_icon 'trash fw'
+          = material_symbol 'delete'
           = t('admin.site_uploads.delete')
 
   .actions