Don't refer to DottyPredef

Author: odersky

sourcecode/jvm/src/test/scala/sourcecode/TestUtil.scala

@@ -6,7 +6,7 @@ object TestUtil {
   lazy val isDotty = {
     val cl: ClassLoader = Thread.currentThread().getContextClassLoader
     try {
-      cl.loadClass("dotty.DottyPredef")
+      cl.loadClass("scala.runtime.Scala3RunTime")
       true
     } catch {
       case _: ClassNotFoundException =>