feat: upgrade Ruby

[btrd]

No description provided.

[ksol]

why the rename of files?

[btrd]

To fix these warnings when running bundle exec jekyll serve --watch --trace --incremental --livereload --livereload-port 4302

          Conflict: The following destination is shared by multiple files.
                    The written file may end up with unexpected contents.
                    /Users/jean_scalingo/Repositories/scalingo/documentation/_site/changelog/security/renew-ssl-certs.html
                     - /Users/jean_scalingo/Repositories/scalingo/documentation/changelog/security/_posts/2015-04-17-renew-ssl-certs.markdown
                     - /Users/jean_scalingo/Repositories/scalingo/documentation/changelog/security/_posts/2016-01-09-renew-ssl-certs.markdown

          Conflict: The following destination is shared by multiple files.
                    The written file may end up with unexpected contents.
                    /Users/jean_scalingo/Repositories/scalingo/documentation/_site/changelog/buildpacks/ruby-updates-multiple-cves.html
                     - /Users/jean_scalingo/Repositories/scalingo/documentation/changelog/buildpacks/_posts/2018-03-29-ruby-updates-multiple-cves.md
                     - /Users/jean_scalingo/Repositories/scalingo/documentation/changelog/buildpacks/_posts/2018-10-22-ruby-updates-multiple-cves.md

          Conflict: The following destination is shared by multiple files.
                    The written file may end up with unexpected contents.
                    /Users/jean_scalingo/Repositories/scalingo/documentation/_site/changelog/databases/redis-4-0-14.html
                     - /Users/jean_scalingo/Repositories/scalingo/documentation/changelog/databases/_posts/2019-04-12-redis-4.0.14.markdown
                     - /Users/jean_scalingo/Repositories/scalingo/documentation/changelog/databases/_posts/2019-05-16-redis-4.0.14.markdown