[rack 3] Deprecation warning emitted Rack::Server is deprecated and replaced by Rackup::Server

[olleolleolle]

What is the current behavior?

The current behavior is "derive from Rack::Server", in Padrino::Server.

That emits a deprecation warning when using Rack 3:

Rack::Server is deprecated and replaced by Rackup::Server

What is the expected behavior?

That there are no deprecation warnings when running on Rack 3.

Which versions of Ruby, Padrino, Sinatra, Rack, OS are you using? Did this work in previous versions?

I assume rack 3.x introduced this, when Rackup gem took the lead in handling config.ru files.