Reduce test configurations by 50%

[MarkEWaite]

Reduce test resource use by testing fewer configurations

Have not seen a failure on Windows specific to Java 11. Since Windows tests run slower and I have fewer Windows machines available, reduce the Windows cases from 3 to 1, testing Java 8 with the default Jenkins
(2.138.1).

Have not seen failures on Linux with the default Jenkins that are not also visible on Windows with default Jenkins. Test Linux with Java 8 and Java 11 using the recent LTS release.

Checklist

• I have read the CONTRIBUTING doc
• Unit tests pass locally with my changes
• I have added documentation as necessary
• No Javadoc warnings were introduced with my changes
• No spotbugs warnings were introduced with my changes
• Any dependent changes have been merged and published in upstream modules (like git-client-plugin)

Types of changes

• Dependency or infrastructure update

If this is a relatively large or complex change, start the discussion by explaining why you chose the solution you did and what alternatives you considered.