docs: update swift format command to reflect the macOS native tests

Author: EchoEllet

README.md

@@ -133,7 +133,7 @@ This package uses [pigeon](https://pub.dev/packages/pigeon) for platform communi
 ```shell
 $ dart run pigeon --input pigeons/messages.dart # To generate the required Dart and host-language code.
 $ dart run build_runner build --delete-conflicting-outputs # To generate the mock classes.
-$ swift-format format --in-place --recursive macos/native_image_picker_macos/Sources/native_image_picker_macos # To format the Swift code.
+$ swift-format format --in-place --recursive macos/native_image_picker_macos/Sources/native_image_picker_macos example/macos/RunnerTests example/macos/RunnerUITests # To format the Swift code.
 ```
 
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