jbake-maven-plugin: No exclusions of direct dependencies supported in Maven

[kwin]

According to https://github.com/jbake-org/jbake/tree/master/jbake-maven-plugin#dependencies

However, if you want your build to only download the bare minimum it needs, you can use to exclude the dependencies you don’t need.

Exclusions in Maven plugins can only be applied on transitive dependencies, not on direct ones (compare with https://issues.apache.org/jira/browse/MNG-6222), so it isn't possible to exclude any of the direct ones from https://github.com/jbake-org/jbake/blob/master/jbake-maven-plugin/build.gradle#L41-L51.