Draft: Upgrade countries gem to v5.0.0

What does this MR do and why?

Related to #383547 (closed)

Upgrade countries gem to the latest version. Required for Ruby 3 upgrade. No longer required for ruby3 compliance as !106533 (merged) (a smaller upgrade) covers this. However we want to remain up-to-date for ISO data consistency purposes 👍

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.