[ruby/json] Append newline at EOF [ci skip]

ruby/json@72e231f929

Author: nobu

ext/json/lib/json/add/string.rb

@@ -32,4 +32,4 @@ def to_json_raw_object
   def to_json_raw(...)
     to_json_raw_object.to_json(...)
   end
-end
+end