Bumps the doc version to 8.16.1

[dedemorton]

DO NOT MERGE UNTIL 8.16.1 IS OFFICIALLY RELEASED

Docs release issue

[github-actions[bot]]

A documentation preview will be available soon.

• 🔨 Buildkite builds
• 📚 HTML diff
• 📙 Preview page

Request a new doc build by commenting

* Rebuild this PR: `run docs-build` * Rebuild this PR and all Elastic docs: `run docs-build rebuild` _{`run docs-build` is much faster than `run docs-build rebuild`. A `rebuild` should only be needed in rare situations. If your PR continues to fail for an unknown reason, the doc build pipeline may be broken. Elastic employees can check the pipeline status [here](https://buildkite.com/elastic/docs-build).}

[dedemorton]

run docs-build