Fix CHANGELOG

When using polyglot-release, it expects the latest URL references HEAd, not main.

Author: mpkorstanje

CHANGELOG.md

@@ -582,7 +582,7 @@ _Although there is no visible change from a user perspective, there are signific
 - [Build] Update Scala versions to 2.11.12 and 2.12.7 ([#11](https://github.com/cucumber/cucumber-jvm-scala/issues/11) Arturas Smorgun)
 
 <!-- Releases -->
-[Unreleased]: https://github.com/cucumber/cucumber-jvm-scala/compare/v8.20.0...main
+[Unreleased]: https://github.com/cucumber/cucumber-jvm-scala/compare/v8.20.0...HEAD
 [8.20.0]:  https://github.com/cucumber/cucumber-jvm-scala/compare/v8.19.0...v8.20.0
 [8.19.0]:  https://github.com/cucumber/cucumber-jvm-scala/compare/v8.18.1...v8.19.0
 [8.18.1]:  https://github.com/cucumber/cucumber-jvm-scala/compare/v8.18.0...v8.18.1