Release 3.47 (#2879)

Minor updates for release 3.47

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I have added sample code updates to the [changelog].
- [x] I updated/added relevant documentation (doc comments with `///`).


If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md
[changelog]: ../CHANGELOG.md

---------

Co-authored-by: Parker Lougheed <parlough@gmail.com>

asset_transformation/grayscale_transformer/bin/grayscale_transformer.dart

@@ -16,8 +16,8 @@ int main(List<String> arguments) {
     ..addOption(outputOptionName, mandatory: true, abbr: 'o');
 
   ArgResults argResults = parser.parse(arguments);
-  final String inputFilePath = argResults[inputOptionName];
-  final String outputFilePath = argResults[outputOptionName];
+  final String inputFilePath = argResults[inputOptionName] as String;
+  final String outputFilePath = argResults[outputOptionName] as String;
 
   try {
     final Image image = decodeImage(File(inputFilePath).readAsBytesSync())!;