Allow sameorigin iframe for help modal

We may want to remove that

config/initializers/secure_headers.rb

@@ -5,7 +5,7 @@ SecureHeaders::Configuration.default do |config|
   }
   # Add "; preload" and submit the site to hstspreload.org for best protection.
   config.hsts = "max-age=#{20.years.to_i}; includeSubdomains"
-  config.x_frame_options = "DENY"
+  config.x_frame_options = "SAMEORIGIN"
   config.x_content_type_options = "nosniff"
   config.x_xss_protection = "1; mode=block"
   config.x_permitted_cross_domain_policies = "none"

spec/features/accessibility/work_packages/work_package_query_spec.rb

@@ -200,6 +200,7 @@ describe 'Work package index accessibility', type: :feature, selenium: true do
 
     context 'help' do
       it 'opens help popup with \'?\'' do
+        expect_angular_frontend_initialized
         find('body').native.send_keys('?')
         expect(page).to have_selector('.ui-dialog', wait: 20)
       end