Revert "Fix generation of wrong json string when field has multiple errors"

This reverts commit a9b666b5.

activemodel/lib/active_model/errors.rb

@@ -168,16 +168,6 @@ def as_json(options=nil)
       self
     end
 
-    def encode_json(encoder)
-      errors = []
-      each_pair do |key, value|
-        value = value.first if value.size == 1
-        errors << "#{encoder.encode(key.to_s)}:#{encoder.encode(value, false)}"
-      end
-
-      "{#{errors * ','}}"
-    end
-
     # Adds +message+ to the error messages on +attribute+, which will be returned on a call to
     # <tt>on(attribute)</tt> for the same attribute. More than one error can be added to the same
     # +attribute+ in which case an array will be returned on a call to <tt>on(attribute)</tt>.

activemodel/test/cases/errors_test.rb

@@ -62,14 +62,4 @@ def self.lookup_ancestors
 
   end
 
-  test 'to_json should return valid json string' do
-    person = Person.new
-    person.errors.add(:name, "can not be blank")
-    person.errors.add(:name, "can not be nil")
-    
-    hash = ActiveSupport::OrderedHash[:name, ["can not be blank", "can not be nil"]]
-    
-    assert_equal person.errors.to_json, hash.to_json
-  end
-
 end