Fix missing package on AssetGenImage.provider()

[yongjhih]

What does this change?

Generated AssetGenImage.provider() => AssetImage(_assetName); should come with package that's consistent with AssetGenImage.image().

AssetGenImage.provider() => AssetImage(_assetName, package: $package);

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• Ensure the tests (melos run unit:test)
• Ensure the analyzer and formatter pass (melos run format to automatically apply formatting)

[yongjhih]

Duplicates to #361