Docs release 16.10

What does this MR do and why?

Creates a docs.gitlab.com release merge request which updates the version dropdown menu for all online versions, updates the archives list, and adds the release to the Docker configuration.

Relates to issue: #1769 (closed)

How to set up and validate locally

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

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.

Merge request 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 merge request.