fix: Remove inactive special interest groups from dropdown

[MarkEWaite]

Remove inactive special interest groups from dropdown

Removed from the documentation site with:

• https://github.com/jenkins-infra/jenkins.io/pull/6296
• https://github.com/jenkins-infra/jenkins.io/pull/6297
• https://github.com/jenkins-infra/jenkins.io/pull/6298
• https://github.com/jenkins-infra/jenkins.io/pull/6299

A cleanup pull request (optional) is removing inactive links

• https://github.com/jenkins-infra/jenkins.io/pull/6300

[jenkins-io-components[bot]]

:tada: This PR is included in version 1.21.1 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket: