Revert "Disable parallelism in the scalacheck suite"
Revert "Disable parallelism in the scalacheck suite"

This reverts commit a6873a2ebe168b14b7742c3030a481c62cc589b9.

reverts PR #6377

This workaround was needed on our 2.12.x branch which remains on sbt
0.13.x, but here on 2.13.x we're on sbt 1 and so this isn't supposed
to be necessary anymore.

martijnhoekstra/scala,scala/scala,scala/scala,lrytz/scala,lrytz/scala,lrytz/scala,martijnhoekstra/scala,martijnhoekstra/scala,martijnhoekstra/scala,scala/scala,scala/scala,martijnhoekstra/scala,lrytz/scala,scala/scala,scala/scala,lrytz/scala,lrytz/scala,martijnhoekstra/scala