Clean up admin UI for accounts (#6004)

* Add staff filter to admin UI for accounts, remove obsolete columns

* Only display OStatus section in admin UI for accounts when OStatus data

app/views/admin/accounts/_account.html.haml

@@ -4,22 +4,11 @@
   %td.domain
     - unless account.local?
       = link_to account.domain, admin_accounts_path(by_domain: account.domain)
-  %td.protocol
-    - unless account.local?
-      = account.protocol.humanize
-  %td.confirmed
+  %td
     - if account.local?
-      - if account.user_confirmed?
-        %i.fa.fa-check
-      - else
-        %i.fa.fa-times
-  %td.subscribed
-    - if account.local?
-      = t('admin.accounts.location.local')
-    - elsif account.subscribed?
-      %i.fa.fa-check
+      = t("admin.accounts.roles.#{account.user&.role}")
     - else
-      %i.fa.fa-times
+      = account.protocol.humanize
   %td
     = table_link_to 'circle', t('admin.accounts.web'), web_path("accounts/#{account.id}")
     = table_link_to 'globe', t('admin.accounts.public'), TagManager.instance.url_for(account)