Warning "illegal reflective access" when used with JDK 11

When using JDK 11 I get the following warning:

```text
14:54:54 [INFO] Using jgitver configuration file: /tmp/workspace/e.kutnot_develop-NAASHCQUDR4LVAYMKRQMG5YDHZTILJZ33S7CQGOI6NFXSMDBVNXQ/.mvn/jgitver.config.xml
14:54:54 [INFO] Using jgitver-maven-plugin [1.8.0] (sha1: 3f3523c5f7540865e3ad66fc9ef1c9daa52a6e6b)
14:54:58 WARNING: An illegal reflective access operation has occurred
14:54:58 WARNING: Illegal reflective access by org.codehaus.groovy.reflection.CachedClass (file:/home/jenkins/m2repo/org/codehaus/groovy/groovy/2.4.21/groovy-2.4.21.jar) to method java.lang.Object.finalize()
14:54:58 WARNING: Please consider reporting this to the maintainers of org.codehaus.groovy.reflection.CachedClass
14:54:58 WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
14:54:58 WARNING: All illegal access operations will be denied in a future release
```

A bit of Google'ing reveals that the warning will disappear if Groovy 3.x or later is used.