Update kubernetes.rb to add versions available

[daodennis]

Previously only the latest and v1.20 was available, this change adds the latest version 1.29 and the previous five versions through 1.24 which are common K8S releases in circulation.

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

TBD on these:

• Updated the versions and releases in the scraper file
• Ensured the license is up-to-date
• 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

[simon04]

Thank you!