Test failure in CommandlineTest#testExecuteBinaryOnPath with Maven 3.5.4 or later

[CommandlineTest#testExecuteBinaryOnPath](
https://github.com/codehaus-plexus/plexus-utils/blob/b762b9963311718f195552686f4675771cfa98fe/src/test/java/org/codehaus/plexus/util/cli/CommandlineTest.java#L106) checks the output of `mvn -version` but it changed with Maven 3.5.4 (due to [MNG-5756](https://issues.apache.org/jira/browse/MNG-5756)) and the test now fails.
