fix(gcs): do not skip signing with `allow_anonymous` #1400

Job	Run time
check_docs	3m 13s
build_all_features	4m 31s
build_all_platforms (ubuntu-latest)	2m 16s
build_default_features (ubuntu-latest)	45s
build_all_platforms (macos-latest)	1m 49s
build_default_features (macos-latest)	34s
build_under_wasm	1m 4s
build_all_platforms (windows-latest)	5m 32s
check_clippy	3m 21s
build_default_features (windows-latest)	2m 13s
check_msrv	28s
unit	6m 18s
	32m 4s

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