Rack::Sendfile config fell out of default template

[jcoyne]

In 6360b73#diff-5c435d953ddbafd6244053b1668c5050568fc41988553bba7b3e5472d47a8242L29-L32
configuration for x_sendfile_header was removed (presumably because Kamal doesn't use it).

However this configuration variable is still used in the default middleware stack:

rails/railties/lib/rails/application/default_middleware_stack.rb

Line 29 in 1b48246

middleware.use ::Rack::Sendfile, config.action_dispatch.x_sendfile_header

Does it make sense to restore it to production.rb.tt for people who still want to configure Rack::Sendfile?

[zzak]

We want to remove it in #44556 anyways, so I think it's fine.

[rails-bot]

This issue has been automatically marked as stale because it has not been commented on for at least three months.
The resources of the Rails team are limited, and so we are asking for your help.
If you can still reproduce this error on the 8-0-stable branch or on main, please reply with all of the information you have about it in order to keep the issue open.
Thank you for all your contributions.

[jcoyne]

I think this is still an issue since #44556 has not progressed in three months.