Use name for Symbol#as_json

Author: jhawthorn

activesupport/lib/active_support/core_ext/object/json.rb

@@ -105,7 +105,7 @@ def as_json(options = nil) # :nodoc:
 
 class Symbol
   def as_json(options = nil) # :nodoc:
-    to_s
+    name
   end
 end