Update the Changelog.md for a v3.8.0-20230127 release

[arm4b]

Based on https://github.com/StackStorm/packer-st2/pull/64, let's do a release and push the latest box to Vagrant cloud.

Just a few final checks that I forgot:

• disconected CircleCI
• new branch protection rules
• missing master branch for the main build
• tag changelog for release