Tag: https://github.com/eclipse-ee4j/angus-activation/releases/tag/2.0.0
Diff: https://github.com/eclipse-ee4j/angus-activation/compare/1.0.0...2.0.0

From the release notes:

Changes module name from com.sun.activation.registries to org.eclipse.angus.activation and package name from com.sun.activation.registries to org.eclipse.angus.activation.

RESTEasy itself does not use these packages directly so this is a safe upgrade. If consumers of RESTEasy are using these, then they need to override the dependency.