Redmine

As you can see in the changelog of Rack, the FastCGI handler has been removed in Rack 3.0.0. This means that Redmine's code to support FastCGI, which relies on Rack::Handler::FastCGI, no longer works.

- Removed antiquated handlers: FCGI, LSWS, SCGI, Thin. ([#1658](https://github.com/rack/rack/pull/1658), [@ioquatix])

It is time to remove the code that no longer works and end support for FastCGI, as FastCGI is no longer a major option for deploying Ruby on Rails applications.