bump sbt-osgi version to 0.9.6, for JDK 15 compat
bump sbt-osgi version to 0.9.6, for JDK 15 compat

scalatest/scalatest,scalatest/scalatest,cheeseng/scalatest,dotty-staging/scalatest,cheeseng/scalatest,scalatest/scalatest,cheeseng/scalatest,dotty-staging/scalatest,dotty-staging/scalatest