Unnecessary new (#20138)

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests
diff --git a/packages/flutter_tools/lib/src/run_cold.dart b/packages/flutter_tools/lib/src/run_cold.dart
index a7fddb2..18a12c5 100644
--- a/packages/flutter_tools/lib/src/run_cold.dart
+++ b/packages/flutter_tools/lib/src/run_cold.dart
@@ -66,7 +66,7 @@
 
     if (flutterDevices.first.observatoryUris != null) {
       // For now, only support one debugger connection.
-      connectionInfoCompleter?.complete(new DebugConnectionInfo(
+      connectionInfoCompleter?.complete(DebugConnectionInfo(
         httpUri: flutterDevices.first.observatoryUris.first,
         wsUri: flutterDevices.first.vmServices.first.wsAddress,
       ));