ActiveJob::Continuation::Step should be eager loaded

Otherwise it will only load in production when running the first
job that defines a step.

We can also force it to be eager loaded, but since it is only ony, there
is no need to do that.

Author: rafaelfranca

activejob/lib/active_job/continuation.rb

@@ -186,7 +186,6 @@ module ActiveJob
   class Continuation
     extend ActiveSupport::Autoload
 
-    autoload :Step
     autoload :Validation
 
     # Raised when a job is interrupted, allowing Active Job to requeue it.
@@ -329,3 +328,5 @@ def instrument(...)
       end
   end
 end
+
+require "active_job/continuation/step"