test: Fix admin signout spec

We need to create a admin user

Author: tvdeyen

spec/features/admin/sign_out_spec.rb

@@ -2,7 +2,7 @@
 
 RSpec.feature "Admin - Sign Out", type: :feature, js: true do
   given!(:user) do
-    create :user, email: "email@person.com"
+    create :admin_user, email: "email@person.com"
   end
 
   background do