Use trusted publishing for releasing to rubygems

[samsimpson1]

Proposed changes

What changed

Use trusted publishing and the standard rubygems/release-gem action to upload gems to rubygems.org.
This removes the need for a static API token, and should hopefully fix the unauthorized errors we've been getting while publishing this gem.

Related issue or tracking reference

No issue for this. It isn't a code change, and the change itself is quite small.

If there is no issue, please open one or please explain why one is not needed (for example small maintenance change, routine dependency update).

Checklist

Before you request approval you should confirm that:

• the pull request has a clear title with a short description about the update in the documentation
• GitHub actions all pass
• you have tested the changes with a fresh build against the latest version of the tech-docs-gem
• you have linked this PR to an issue (or explained why none exists)
• you have updated documentation if needed