Prepare final release notes for 6.0.0-dev20 (#6848)

Author: eddyashton

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - CA certificate bundles used for JWT refresh and containing more than one certificate are now handled correctly (#6817).
 - Memory leak during EC key creation is fixed (#6845).
 - Fixed thread-safety issues when CCF nodes attempted to contact non-TLS servers. This previously could cause errors when running SNP builds with multiple worker threads (#6836).
+- SNP nodes will no longer crash when run on firmware returning v3 attestations (#6841).
 
 ## [6.0.0-dev19]