[tests/isolate] Avoid use of deprecated unmodifiable typed data view constructor

Issue: #53785
Change-Id: I205492adcec6432f5503cbf9f015a6ac2e9d6f5c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/332165
Reviewed-by: Martin Kustermann <[email protected]>
Commit-Queue: Martin Kustermann <[email protected]>

Author: rakudrama

tests/lib/isolate/unmodifiable_typed_data_pass_by_copy_test.dart

@@ -10,7 +10,7 @@ import "package:expect/expect.dart";
 
 main() {
   final backing = new Uint8List(1);
-  final original = new UnmodifiableUint8ListView(backing);
+  final original = backing.asUnmodifiableView();
   var port;
   port = new RawReceivePort((copy) {
     port.close();

tests/lib_2/isolate/unmodifiable_typed_data_pass_by_copy_test.dart

@@ -12,7 +12,7 @@ import "package:expect/expect.dart";
 
 main() {
   final backing = new Uint8List(1);
-  final original = new UnmodifiableUint8ListView(backing);
+  final original = backing.asUnmodifiableView();
   var port;
   port = new RawReceivePort((copy) {
     port.close();