Remove forgotten code from spec

Commit e4ebeb8a29 forgot to remove this
code.

spec/features/admin/enterprise_user_spec.rb

@@ -6,7 +6,6 @@ feature %q{
 } do
   include AuthenticationWorkflow
   include WebHelper
-  include AdminHelper
 
   let!(:user) { create_enterprise_user }
   let!(:supplier1) { create(:supplier_enterprise, name: 'Supplier 1') }

spec/support/request/admin_helper.rb

@@ -1,8 +1,4 @@
 module AdminHelper
-  def have_admin_menu_item(menu_item_name)
-    have_selector "ul[data-hook='admin_tabs'] li", text: menu_item_name
-  end
-
   def toggle_columns(*labels)
     # open dropdown
     find("div#columns-dropdown", text: "COLUMNS").click