Repository: flutter
Issue: Autofill Hints iOS:`Choose My Own Password` option doesn't clear text field
Labels: a: text input,platform-ios,framework,f: material design,has reproducible steps,P2,found in release: 2.2,found in release: 2.3,customer: flex,team-text-input,triaged-text-input

## Steps to Reproduce

1. Run on iOS device
2. Focus the password text field
3. Tap 'Choose My Own Password'
4. Text field does not clear

https://user-images.githubusercontent.com/666539/121722066-f77bb080-cab2-11eb-8265-9d931ca23792.mov


## MCVE

```dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(SpikeApp());
}

class SpikeApp extends StatelessWidget {
  const SpikeApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: _HomeScreen(),
    );
  }
}

class _HomeScreen extends StatefulWidget {
  const _HomeScreen({Key? key}) : super(key: key);

  @override
  __HomeScreenState createState() => __HomeScreenState();
}

class __HomeScreenState extends State<_HomeScreen> {
  final emailController = TextEditingController();
  final passwordController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    final spacer = SizedBox(height: 25);

    return Scaffold(
      body: SafeArea(
        child: Padding(
          padding: const EdgeInsets.all(25),
          child: AutofillGroup(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                Text('Create account'),
                spacer,
                TextField(
                  controller: emailController,
                  autofillHints: [
                    AutofillHints.email,
                  ],
                  textInputAction: TextInputAction.next,
                  decoration: InputDecoration(
                    hintText: 'Your email',
                  ),
                ),
                spacer,
                TextField(
                  controller: passwordController,
                  autofillHints: [
                    AutofillHints.newPassword,
                  ],
                  decoration: InputDecoration(
                    hintText: 'Your password',
                  ),
                ),
                spacer,
                ElevatedButton(
                  child: Text('Save account info'),
                  onPressed: () {
                    TextInput.finishAutofillContext();
                  },
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}
```

### flutter doctor
```
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.2.1, on macOS 11.4 20F71 darwin-x64, locale en-US)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] VS Code (version 1.57.0)
[✓] Connected device (3 available)

• No issues found!
```