Downgrade com.google.gms:google-services back to 4.3.15, since 4.4.2 appear to break firestore

The Firestore build error is 

```
firestore/src/androidTest/java/com/google/firebase/firestore/testutil/prod_provider/FirestoreProvider.java:39: error: cannot find symbol
    return context.getString(R.string.project_id);
                              ^
  symbol:   variable string
  location: class R
```

Author: dconeybe

gradle/libs.versions.toml

@@ -28,7 +28,7 @@ firebaseComponents = "18.0.0"
 firebaseCrashlyticsGradle = "3.0.2"
 glide = "4.11.0"
 googleApiClient = "1.30.9"
-googleServices = "4.4.2"
+googleServices = "4.3.15"
 gradleErrorpronePlugin = "3.1.0"
 grpc = "1.62.2"
 grpcKotlin = "1.4.1"