Updates runtime (#20)

* Updates scala-exercises runtime library

* Updates runtime

Author: juanpedromoreno

build.sbt

@@ -16,7 +16,7 @@ lazy val V = new {
   val collectioncompat: String    = "2.1.6"
   val github4s: String            = "0.24.1"
   val http4s: String              = "0.21.6"
-  val runtime: String             = "0.6.0"
+  val runtime: String             = "0.6.3"
   val scala: String               = "2.13.3"
   val scala212: String            = "2.12.11"
   val scalacheck: String          = "1.14.3"