Update Scala version to 2.13.0-M4-pre-20d3c21

Author: lrytz

build.sbt

@@ -7,14 +7,14 @@ name    := "scala-partest"
 version := "1.1.4-SNAPSHOT"
 
 scalaVersionsByJvm in ThisBuild := {
-  val vs = List("2.12.4", "2.13.0-M3")
+  val vs = List("2.13.0-M4-pre-20d3c21")
 
   Map(
     8 -> vs.map(_ -> true),
     9 -> vs.map(_ -> false))
 }
 
-scalaXmlVersion := "1.0.6"
+scalaXmlVersion := "1.1.0-newCollectionsBootstrap"
 
 scalacOptions += "-Xfatal-warnings"
 enableOptimizer