[#1504] update RELEASE-NOTES.md

RELEASE-NOTES.md

@@ -39,6 +39,7 @@ Picocli follows [semantic versioning](http://semver.org/).
 * [#1457] DOC: add caution about arguments in @files with quoted option parameters. Thanks to [Andreas Deininger](https://github.com/deining) for the pull request.
 * [#1461] BUILD: Allow publishing without signing for non-release versions. Thanks to [Andreas Deininger](https://github.com/deining) for raising this.
 * [#1459] BUILD: The nexus-staging Gradle plugin must be applied to the root project, not to subprojects. Thanks to [Andreas Deininger](https://github.com/deining) for raising this.
+* [#1504] BUILD: Run tests on Java 5/6/7 in CI environment.
 * [#1495] DEP: Bump validation-api from 2.0.0.Final to 2.0.1.Final
 * [#1496] DEP: Bump biz.aQute.bnd.gradle from 5.1.2 to 6.1.0
 * [#1494] DEP: Bump kotlin-gradle-plugin from 1.5.31 to 1.6.0