Fix a couple of analyzer warnings

* Unused import in editable_text.dart
* Type mismatch in append_child_test.dart

packages/flutter/lib/src/fn3/editable_text.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:sky' as sky;
 
 import 'package:mojo_services/keyboard/keyboard.mojom.dart';
 import 'package:sky/painting.dart';

packages/unit/test/engine/append_child_test.dart

@@ -16,7 +16,7 @@ void main() {
       parent.appendChild(null);
     }, throws);
     expect(() {
-      parent.appendChild({"tagName": "div"});
+      Function.apply(parent.appendChild, [{"tagName": "div"}]);
     }, throws);
   });