Remove unused public static members of private classes/enums (#48218)

dev/manual_tests/lib/density.dart

@@ -158,8 +158,6 @@ class Options extends StatefulWidget {
 }
 
 class _OptionsState extends State<Options> {
-  static final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
-
   @override
   void initState() {
     super.initState();

packages/flutter/lib/src/services/platform_views.dart

@@ -422,7 +422,6 @@ enum _AndroidViewState {
   waitingForSize,
   creating,
   created,
-  createFailed,
   disposed,
 }
 

packages/flutter/test/foundation/bit_field_test.dart

@@ -7,6 +7,7 @@
 import 'package:flutter/foundation.dart';
 import '../flutter_test_alternative.dart';
 
+// ignore: unused_field
 enum _TestEnum { a, b, c, d, e, f, g, h, }
 
 void main() {