Update Firebase games Podfiles to use Firebase 6.16.0
Update Firebase games Podfiles to use Firebase 6.16.0

PiperOrigin-RevId: 294254094

firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk,firebase/firebase-cpp-sdk