Fix IP blocks in admin panel

It was broken due to discrepancies between upstream and glitch-soc's
theming system.

app/views/admin/ip_blocks/index.html.haml

@@ -1,9 +1,6 @@
 - content_for :page_title do
   = t('admin.ip_blocks.title')
 
-- content_for :header_tags do
-  = javascript_pack_tag 'admin', integrity: true, async: true, crossorigin: 'anonymous'
-
 - if can?(:create, :ip_block)
   - content_for :heading_actions do
     = link_to t('admin.ip_blocks.add_new'), new_admin_ip_block_path, class: 'button'