Implement required #encode_with

While running the spec `ARCONN=mysql2 ruby -v -Itest
test/cases/yaml_serialization_test.rb`
the following warning shows up:
`implementing to_yaml is deprecated, please implement "encode_with"`

activerecord/lib/active_record/relation/delegation.rb

@@ -119,6 +119,10 @@ module ActiveRecord
         arel.respond_to?(method, include_private)
     end
 
+    def encode_with(coder)
+      coder.represent_seq(nil, to_a)
+    end
+
     protected
 
     def array_delegable?(method)

activerecord/test/cases/yaml_serialization_test.rb

@@ -1,5 +1,6 @@
 require 'cases/helper'
 require 'models/topic'
+require 'models/reply'
 require 'models/post'
 require 'models/author'