Upgrade to Corda 4 test docs only have Kotlin examples

https://docs.corda.r3.com/releases/master/app-upgrade-notes.html?highlight=corda%20upgrade%20notes#step-7-possibly-adjust-test-code

True in O/S too: https://docs.corda.net/app-upgrade-notes.html#step-7-possibly-adjust-test-code

Currently only has Kotlin based examples.