Ruby gem and package.json upgrades

[JC-DSIT]

Proposed changes

What changed

• remove gem pins that are not required
• up required ruby version

A number of packages are pinned unnecessarily. Many of these have not been active for some time and the latest (i.e last) version is compatible. The ruby version in the spec needs updating to match the .ruby-version used by github actions and in the example site

Related issue or tracking reference

This does not relate to a specific issue or fix, but is general maintenance to allow future planning of how to manage the gema nd upgrade to a more recent ruby version etc

Screenshots or examples (if relevant)

Include screenshots, logs, or rendered output if this change affects layout or behaviour.

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