Update build scripts for example app.

[ndahlquist]

Before this change set, I am unable to build the example app with Flutter 3.0.5 (latest stable version):

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Warning
──────────────────────────────────────────────────────────────────────────────
Your Flutter application is created using an older version of the Android
embedding. It is being deprecated in favor of Android embedding v2. Follow the
steps at

https://flutter.dev/go/android-project-migration

to migrate your project. You may also pass the --ignore-deprecation flag to
ignore this check and continue with the deprecated v1 embedding. However,
the v1 Android embedding will be removed in future versions of Flutter.
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
The detected reason was:

  /Users/nic/swarm_workspace/third_party/social_embed_webview/example/android/app/src/main/AndroidManifest.xml uses `android:name="io.flutter.app.FlutterApplication"`
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Build failed due to use of deprecated Android v1 embedding.

(various other errors were also encountered after this one).

After this change, the app builds correctly for me.