lang/ruby27: throw out racc from lang/ruby27

because racc is provied as "default gem" since Ruby 2.7 [1].

We provide default gems as gem ports rather than a part of lang/ruby* port.
files/patch-tool_rbinstall.rb does that. bin/*racc* are leftover wrapper
script that the patch didn't remove default gem racc completely.

racc is provided by devel/rubygem-racc. To avoid conflict racc gem port vs
ruby port, throw it out completely from ruby port.

[1] https://ruby-trunk-changes.hatenablog.com/entry/ruby_trunk_changes_20190620

PR: 242359 237833
Submitted by: Yasuhiro KIMURA <yasu@utahime.org> (based on)