Remove unnecessary main.

Author: DarkDimius

compiler/src/dotty/tools/dotc/config/Properties.scala

@@ -135,4 +135,10 @@ trait PropertiesTrait {
     }
     okVersions exists (javaVersion startsWith _)
   }
+
+  // provide a main method so version info can be obtained by running this
+  def main(args: Array[String]): Unit = {
+    val writer = new PrintWriter(Console.err, true)
+    writer println versionMsg
+  }
 }