Bump firebase_auth in /in_app_purchases/step_09/app

Bumps [firebase_auth](https://github.com/FirebaseExtended/flutterfire) from 3.3.15 to 3.3.16.
- [Release notes](https://github.com/FirebaseExtended/flutterfire/releases)
- [Changelog](https://github.com/firebase/flutterfire/blob/master/CHANGELOG.md)
- [Commits](firebase/flutterfire@firebase_auth-v3.3.15...firebase_auth-v3.3.16)

---
updated-dependencies:
- dependency-name: firebase_auth
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

in_app_purchases/step_09/app/pubspec.lock

@@ -105,7 +105,7 @@ packages:
       name: firebase_auth
       url: "https://pub.dartlang.org"
     source: hosted
-    version: "3.3.15"
+    version: "3.3.16"
   firebase_auth_platform_interface:
     dependency: transitive
     description:

in_app_purchases/step_09/app/pubspec.yaml

@@ -10,7 +10,7 @@ dependencies:
   cloud_firestore: ^3.1.13
   cloud_functions: ^3.2.13
   cupertino_icons: ^1.0.2
-  firebase_auth: ^3.3.15
+  firebase_auth: ^3.3.16
   firebase_core: ^1.15.0
   flutter:
     sdk: flutter