Address overlooked comment

Author: odersky

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -1281,7 +1281,7 @@ class TreeUnpickler(reader: TastyReader,
         if (arg.isTerm) new TastyTreeExpr(arg)
         else new TreeType(arg)
       val reifiedArgs = args.map(wrap)
-      var filled = if (isType) {
+      val filled = if (isType) {
         val quotedType = splice.asInstanceOf[Seq[Any] => quoted.Type[_]](reifiedArgs)
         PickledQuotes.quotedTypeToTree(quotedType)
       } else {