Sync changelog with docs editor updates

[kaylareopelle]

The biggest change here is the removal of the overview sentence. If I remember correctly, the overview sentence used to help us on the page that displayed all of the Release Notes on the docs website.

Now that the Release Notes page does not feature snippets, but instead shows the entire release notes, I don't think we need it anymore.

• 9.16.0 release notes: https://docs.newrelic.com/docs/release-notes/agent-release-notes/ruby-release-notes/ruby-agent-9-16-0/
• Release notes page: https://docs.newrelic.com/docs/release-notes/agent-release-notes/ruby-release-notes
• Old release notes structure: https://web.archive.org/web/20230205165159/https://docs.newrelic.com/docs/release-notes/agent-release-notes/ruby-release-notes/

[github-actions[bot]]

SimpleCov Report

	Coverage	Threshold
Line	93.87%	93%
Branch	69.81%	50%