Update v0.20.md

Author: hacdias

docs/changelogs/v0.20.md

@@ -12,6 +12,7 @@
     - [Improved testing](#improved-testing)
     - [Trace Context support](#trace-context-support)
     - [Removed legacy features](#removed-legacy-features)
+  - [`--empty-repo` is now the default](#--empty-repo-is-now-the-default)
 - [📝 Changelog](#-changelog)
 - [👨‍👩‍👧‍👦 Contributors](#-contributors)