devel/ruby-parser: update to 3.20.3

3.20.3 (2023-07-11)

2 minor enhancements:

* Added Parser#in_argdef and integrated into 3.x parsers.
* Improved tools/munge.rb to handler MRI 3.2 output

2 bug fixes:

* Fixed process_dots to properly deal with paren-less forward_args. (eric1234)
* Fixed tools/ripper.rb to properly print ripper sexp at the end

(taca)