Null safety cleanup in test runner code (#2661)

Author: nshahan

frontend_server_client/example/web_client.dart

@@ -27,7 +27,6 @@ void main(List<String> args) async {
       '--multi-root-scheme=org-dartlang-sdk',
       '--modules=amd',
       '--module-name=dart_sdk',
-      '--sound-null-safety',
       '-o',
       dartSdkJs,
       p.url.join(sdkDir, sdkKernelPath),

frontend_server_common/lib/src/devfs.dart

@@ -29,7 +29,6 @@ class WebDevFS {
     required this.projectDirectory,
     required this.packageUriMapper,
     required this.index,
-    this.soundNullSafety = true,
     this.urlTunneler,
     required this.sdkLayout,
     required this.compilerOptions,
@@ -46,9 +45,6 @@ class WebDevFS {
   List<Uri> sources = <Uri>[];
   DateTime? lastCompiled;
 
-  @Deprecated('Only sound null safety is supported as of Dart 3.0')
-  final bool soundNullSafety;
-
   final TestSdkLayout sdkLayout;
   final CompilerOptions compilerOptions;
 

frontend_server_common/lib/src/frontend_server_client.dart

@@ -394,7 +394,6 @@ class ResidentCompiler {
       ],
       if (useDebuggerModuleNames) '--debugger-module-names',
       '--experimental-emit-debug-metadata',
-      '--sound-null-safety',
       for (final experiment in compilerOptions.experiments)
         '--enable-experiment=$experiment',
       if (compilerOptions.canaryFeatures) '--dartdevc-canary',

test_common/lib/test_sdk_configuration.dart

@@ -14,11 +14,8 @@ import 'package:test_common/test_sdk_layout.dart';
 /// Implementation for SDK configuration for tests that can generate
 /// missing assets.
 ///
-///  - Generate SDK js, source map, and full dill (normally included in flutter
-///    SDK or produced by build).
-///
-/// TODO(annagrin): update to only generating missing sound artifacts
-/// for frontend server after we have no uses of weak null safety.
+///  - Generate SDK js, source map (normally included in flutter SDK
+///    or produced by build).
 class TestSdkConfigurationProvider extends SdkConfigurationProvider {
   final _logger = Logger('TestSdkConfigurationProvider');