Apply suggestion from @lmolkova

Author: lmolkova

util/opentelemetry-util-genai/CHANGELOG.md

@@ -7,7 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
-## Version 0.4b0 (2026-04-30)
+## Version 0.4b0 (2026-05-01)
 
 - Add `AgentInvocation` type with `invoke_agent` span lifecycle
   ([#4274](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/4274))