Update Ruby, Rails, and Minitest docs

[larouxn]

Heavily based on the following.

• doc: ruby (and related) update #1902

If you're updating existing documentation to its latest version, please ensure that you have:

• Updated the versions and releases in the scraper file
• Ensured the license is up-to-date and that the documentation's entry in the array in about_tmpl.coffee matches its data in self.attribution
• Ensured the icons and the SOURCE file in public/icons/your_scraper_name/ are up-to-date if the documentation has a custom icon
• Ensured self.links contains up-to-date urls if self.links is defined
• Tested the changes locally to ensure:
  • The scraper still works without errors
  • The scraped documentation still looks consistent with the rest of DevDocs
  • The categorization of entries is still good

Sources

• https://www.ruby-lang.org/en/downloads/releases/
• https://rubyonrails.org/category/releases
• https://github.com/minitest/minitest/tags

[larouxn]

👋 @simon04, perhaps you could have a look at this when you have a moment. 🙇‍♂️

[simon04]

Thank you!