Deprecated version

During the running I see the error in console:

> The plugin `flutter_webview_plugin` uses a deprecated version of the Android embedding.
> To avoid unexpected runtime failures, or future build failures, try to see if this plugin supports the Android V2 embedding. Otherwise, consider removing it since a future release of Flutter will remove these deprecated APIs.
> If you are plugin author, take a look at the docs for migrating the plugin to the V2 embedding: https://flutter.dev/go/android-plugin-migration.
Please, upgrade the plugin

## System info

Issue occurs on: Android
Plugin version: 0.4.0
Flutter doctor output:

```
Flutter (Channel stable, 2.8.0, on macOS 11.6.1 20G224 darwin-x64, locale en-PL)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 13.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] IntelliJ IDEA Ultimate Edition (version 2020.3)
[✓] VS Code (version 1.63.0)
[✓] Connected device (2 available)```

## Steps to Reproduce

1. Just run any app with Flutter version 2.8.0. Android 30.0.3

Start with the linked Flutter Android plugin migration guide and reproduce the warning by running an app with Flutter 2.8.0 on Android. Review the plugin's Android implementation and migrate it to the V2 embedding; done means the app runs without the deprecated-embedding warning.

Written by the indexing model from the issue text.