Fix argument error

https://github.com/dtao/safe_yaml isn't maintained for 4 years, so we folk and patch/maintained it ourselves.

Passing filename with the 2nd argument of Psych.parse is deprecated.
Use keyword argument like Psych.parse(yaml, filename: ...) instead.'
https://github.com/ruby/psych/blob/0abce07b908fa0128223a3e11f2eeb4be0c191d6/lib/psych.rb#L386