include Spark 3.0.0 preview in spark_version_latest (#2394)
include Spark 3.0.0 preview in spark_version_latest (#2394)

include Spark 3.0.0 preview in spark_version_latest

Signed-off-by: yl790 <506e136862ca6a2cd6209c2ab7376874a235e7c2@rstudio.com>
rstudio/sparklyr,rstudio/sparklyr,rstudio/sparklyr,rstudio/sparklyr