Do not alias_method_chain Class#inherited

If anohter module overrides Class#inherited after aliased,
the orverided inherited method is not called.

```ruby
module FooConcern
  extend ActiveSupport::Concern

  module ClassMethods
    
    # this method is not called when subclass defined
    def inherited(subclass)
      puts "test"
      super subclass
    end
  end
end

class ActiveRecord::Base
  include FooConcern
end

class Foo < ActiveRecord::Base ; end
# => FooConcern's inherited is not called
```

I think it would simply overrides Class#inherited like other gems.

i.e) https://github.com/rails/rails-observers/blob/master/lib/rails/observers/active_model/observing.rb#L197