warning: [deprecation] getFlutterEngine() in FlutterPluginBinding has been deprecated

This issue is filed for visibility. Presumably you can ignore this error when hacking on cone.

When building the android app, I see the following warning:

```
~/.pub-cache/hosted/pub.dartlang.org/shared_preferences-0.5.6/android/src/main/java/io/flutter/plugins/sharedpreferences/SharedPreferencesPlugin.java:25: warning: [deprecation] getFlutterEngine() in FlutterPluginBinding has been deprecated
setupChannel(binding.getFlutterEngine().getDartExecutor(), binding.getApplicationContext());
^
1 warning
```

The directly related issue is https://github.com/flutter/flutter/issues/44569, closed as duplicate of https://github.com/flutter/flutter/issues/44070. EDIT: In turn, closed as duplicate of https://github.com/flutter/flutter/issues/47153.

I would like to take a closer look at the status of the issue at some point, but I think we more or less have to wait.

The warning comes from the shared_preferences plugin's Android file, SharedPreferencesPlugin.java; start by checking the referenced Flutter issue 47153 and the plugin status. Done would require the upstream deprecation to be addressed so the Android build no longer reports this warning, but the issue says to wait.

Written by the indexing model from the issue text.