Log Message:
textproc/ruby-rdiscount: update to 2.2.0.2

Update ruby-rdiscount package to 2.2.0.2.

2.2.0.2 (August 9, 2020)

* Fix compilation error on macOS Big Sur Preview (11.0).
* Enable continuous integration with Ruby 2.4-2.6.
* Builds with Ruby 2.7.0 locally but not on Travis CI.