Update Jenkinsfile

[zbynek]

• Please check if the PR fulfills these requirements

• [x] The commit message describes your change

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

This does not introduce any change to the plugin itself, but allows contributors to check their changes against newer versions of Jenkins and JVM.

By merging this PR it should be possible to check that CI passes for #317 -- the reason for separate PRs is that my changes in Jenkinsfile will be ignored until they are merged to the default branch.

• What is the current behavior? (You can also link to an open issue here)

Plugin is built with Java 8 against Jenkins 2.102

• What is the new behavior (if this is a feature change)?

Plugin is build with Java 11 and 17 against Jenkins version defined in POM

[zbynek]

@hoegertn could you please merge this one so that I can check if there's still something to do for #317 ?