fix(deps): update dependency firebase_auth_platform_interface to v8

Author: renovate[bot]

pubspec.yaml

@@ -15,7 +15,7 @@ dependencies:
   # Firebase
   firebase_core: ^3.4.0
   firebase_auth: ^5.2.0
-  firebase_auth_platform_interface: ^7.0.0
+  firebase_auth_platform_interface: 8.1.8
 
   # Firebase Authentications
   google_sign_in: ^6.2.1