[M56] Update iOS pods to 6.9.0
[M56] Update iOS pods to 6.9.0

PiperOrigin-RevId: 270716454

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