use request_admin_user

use helper method instead of calling out the miq_request_approval role
(yes, this is being corrected in this commit)

https://bugzilla.redhat.com/show_bug.cgi?id=1608554

app/helpers/application_helper/button/miq_request_delete.rb

@@ -4,7 +4,7 @@ class ApplicationHelper::Button::MiqRequestDelete < ApplicationHelper::Button::M
 
   def disabled?
     requester = current_user
-    return false if requester.role_allows?(:feature => "miq_request_superadmin")
+    return false if requester.miq_user_role.request_admin_user?
     @error_message = _("Users are only allowed to delete their own requests") if requester.name != @record.requester_name
     if %w(approved denied).include?(@record.approval_state)
       @error_message = _("%{approval_states} requests cannot be deleted") %