Issue #11893 fix maven helloworld example

[janbartel]

Closes #11893

Update helloworld maven example

[olamy]

Sadly, we do not have an automatic way to validate those code fragments via compilation :( (grabbing code fragment from a source file located in github and building via the project)

I cannot find any extension here https://github.com/asciidoctor/asciidoctor.org/blob/main/docs/extensions.adoc
Maybe writing an extension for this?

hehe, please note it's possible with Old Good Maven :P https://maven.apache.org/doxia/macros/index.html#snippet-macro