Remove highly uncommon option for moving the manifest path

railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt

@@ -20,9 +20,6 @@
 
   # Generate digests for assets URLs.
   config.assets.digest = true
-
-  # Defaults to nil and saved in location specified by config.assets.prefix
-  # config.assets.manifest = YOUR_PATH
   <%- end -%>
 
   # Specifies the header that your server uses for sending files.