Require active_support's delegation module (fix crash introduced in 0.9.0)

[aaronjensen]

#188 caused an error when applications that don't load all of Rails first before loading Propshaft are started:

gems/ruby/3.3.0/gems/propshaft-0.9.0/lib/propshaft/compiler.rb:6:in `<class:Compiler>': undefined method `delegate' for class Propshaft::Compiler (NoMethodError)

  delegate :config, :load_path, to: :assembly
  ^^^^^^^^
Did you mean?  DelegateClass
        from gems/ruby/3.3.0/gems/propshaft-0.9.0/lib/propshaft/compiler.rb:4:in `<main>'
 

Propshaft appears to only load the ActiveSupport extensions it needs, which is great, but this one is now missing.

Alternatively, the use of delgate can be replaced with a method, but I have a sense that this change is more appropriate for this project.