Maven AsciiDoc plugin should not show warnings during the build

[martinmo]

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[INFO] --- asciidoctor-maven-plugin:2.2.1:process-asciidoc (html) @ lab-kickstart ---
[INFO] sourceDirectory /Users/martin/Code/stlab/meta/kickstart/src/docs/asciidoc does not exist
[INFO] sourceDirectory /Users/martin/Code/stlab/meta/kickstart/src/asciidoc does not exist
2022-10-21T10:14:19.868+02:00 [main] WARN FilenoUtil : Native subprocess control requires open access to the JDK IO subsystem
Pass '--add-opens java.base/sun.nio.ch=ALL-UNNAMED --add-opens java.base/java.io=ALL-UNNAMED' to enable.
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] Using 'UTF-8' encoding to copy filtered properties files.
...