Update docs framework and messaging to align with updated engineering maintenance policy

[karenzone]

"With the release of 8.16, we are also enhancing our Engineering Maintenance Policy. Elastic will now maintain the most current minor version as well as the previous minor version. This change increases the time customers can remain on a recent minor version and continue receiving maintenance updates. This is huge for our customers."

• Priority 1: Remove the "no additional bug fixes or documentation updates" messaging for the previous minor. This messaging directly contradicts the new maintenance policy.

  

• Evaluate pros and cons of including the previous minor in the version dropdown. Consider SEO and other implications.

  

• Communicate to all Docs team members that we should be backporting to the previous minor in addition to current version.