Update scripts workers to be compatible with Scala 3 (#1352)

Author: liucijus

src/scala/scripts/ScalaPBWorker.scala

@@ -38,7 +38,7 @@ object ScalaPBWorker extends Worker.Interface {
 
   def main(args: Array[String]): Unit = Worker.workerMain(args, ScalaPBWorker)
 
-  def work(args: Array[String]) {
+  def work(args: Array[String]): Unit = {
     val code = ProtocBridge.runWithGenerators(protoc, generators, args)
     if (code != 0) {
       sys.error(s"Exit with code $code")

src/scala/scripts/ScroogeWorker.scala

@@ -21,7 +21,7 @@ object ScroogeWorker extends Worker.Interface {
       case e: Exception => ()
     }
 
-  def work(args: Array[String]) {
+  def work(args: Array[String]): Unit = {
     def getIdx(i: Int): List[String] = {
       if (args.size > i) {
         // bazel worker arguments cannot be empty so we pad to ensure non-empty