migrate to `package:async` unawaited

Change-Id: I48cc9c0b2d16ecc50b3b7d1ea68006388e041a08
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/214684
Reviewed-by: Ben Konyi <bkonyi@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>
diff --git a/pkg/dartdev/lib/dartdev.dart b/pkg/dartdev/lib/dartdev.dart
index 151bf0a..73cf9c2 100644
--- a/pkg/dartdev/lib/dartdev.dart
+++ b/pkg/dartdev/lib/dartdev.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 // Do not call exit() directly. Use VmInteropHandler.exit() instead.
+import 'dart:async';
 import 'dart:io' as io hide exit;
 import 'dart:isolate';
 
@@ -12,7 +13,6 @@
 import 'package:dart_style/src/cli/format_command.dart';
 import 'package:devtools_server/devtools_server.dart';
 import 'package:meta/meta.dart';
-import 'package:pedantic/pedantic.dart';
 import 'package:pub/pub.dart';
 import 'package:usage/usage.dart';
 
diff --git a/pkg/dartdev/pubspec.yaml b/pkg/dartdev/pubspec.yaml
index fb3e6d0..9fbdb4b 100644
--- a/pkg/dartdev/pubspec.yaml
+++ b/pkg/dartdev/pubspec.yaml
@@ -28,7 +28,6 @@
   nnbd_migration:
     path: ../nnbd_migration
   path: any
-  pedantic: any
   pub: any
   telemetry:
     path: ../telemetry