X-Permitted-Cross-Domain-Policies was listed twice

See 32bb3f5#commitcomment-16319052

✨ @reedloden for the 👀

Author: oreoshake

lib/secure_headers/railtie.rb

@@ -7,7 +7,7 @@ class Railtie < Rails::Railtie
                              'X-Permitted-Cross-Domain-Policies', 'X-Download-Options',
                              'X-Content-Type-Options', 'Strict-Transport-Security',
                              'Content-Security-Policy', 'Content-Security-Policy-Report-Only',
-                             'X-Permitted-Cross-Domain-Policies', 'Public-Key-Pins', 'Public-Key-Pins-Report-Only']
+                             'Public-Key-Pins', 'Public-Key-Pins-Report-Only']
 
       initializer "secure_headers.middleware" do
         Rails.application.config.middleware.use SecureHeaders::Middleware