Remove recommendation to use deprecated fetchSignInMethods #8116

Job	Run time
Check changed files	0s
binary_size_metrics (iOS)	5m 56s
pod-lib-lint-abtesting (iOS)	10m 10s
pod-lib-lint-auth (iOS)	10m 46s
pod-lib-lint-database (iOS)	15m 2s
pod-lib-lint-firestore (iOS)	21m 34s
pod-lib-lint-dynamiclinks (iOS)	6m 55s
pod-lib-lint-inappmessaging (iOS)	11m 40s
pod-lib-lint-functions (iOS)	4m 35s
pod-lib-lint-messaging (iOS)	11m 57s
pod-lib-lint-performance (iOS)	12m 9s
pod-lib-lint-remoteconfig (iOS)	10m 52s
pod-lib-lint-storage (iOS)	7m 41s
create_report	3m 1s
	2h 12m 18s

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