Add placeholder `GoogleService-Info.plist` to Vertex AI sample #9089

Job	Run time
Check changed files	0s
pod-lib-lint-auth (iOS)	7m 4s
pod-lib-lint-abtesting (iOS)	7m 45s
pod-lib-lint-database (iOS)	11m 7s
pod-lib-lint-dynamiclinks (iOS)	6m 15s
pod-lib-lint-firestore (iOS)	30m 52s
pod-lib-lint-functions (iOS)	2m 36s
pod-lib-lint-inappmessaging (iOS)	5m 39s
pod-lib-lint-messaging (iOS)	12m 22s
pod-lib-lint-performance (iOS)	7m 13s
pod-lib-lint-remoteconfig (iOS)	8m 7s
pod-lib-lint-storage (iOS)	11m 4s
create_report	3m 21s
	1h 53m 25s

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