firestore.cmake: update pinned commit

Author: dconeybe

cmake/external/firestore.cmake

@@ -24,7 +24,7 @@ ExternalProject_Add(
 
   DOWNLOAD_DIR ${FIREBASE_DOWNLOAD_DIR}
   GIT_REPOSITORY https://github.com/firebase/firebase-ios-sdk
-  GIT_TAG 0ed860a0360735c28a26aad9cbe899695009a236
+  GIT_TAG 865162a0355a788728edf6798bcca5218dd50734
   GIT_SHALLOW ON
 
   PREFIX ${PROJECT_BINARY_DIR}