Bump docker/login-action from 3.0.0 to 3.1.0 #49

Job	Run time
shellcheck	16s
Run tests (gantry_cleanup_images_spec.sh)	2m 8s
Run tests (gantry_common_options_spec.sh)	1m 40s
Run tests (gantry_filters_spec.sh)	1m 13s
Run tests (gantry_login_spec.sh)	2m 8s
Run tests (gantry_manifest_spec.sh)	1m 43s
Run tests (gantry_notify_spec.sh)	1m 27s
Run tests (gantry_parallel_spec.sh)	2m 1s
Run tests (gantry_rollback_spec.sh)	1m 5s
Run tests (gantry_service_multiple_spec.sh)	2m 4s
Run tests (gantry_service_no_running_tasks_spec.sh)	1m 33s
Run tests (gantry_service_single_spec.sh)	1m 37s
Run tests (gantry_update_options_spec.sh)	1m 39s
	20m 34s

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