Fix user journey doc's image link
Fix user journey doc's image link

PiperOrigin-RevId: 358155961
Change-Id: Ief39c0b7ff1ce4be765086ca6425e2b59eefa986

GoogleCloudPlatform/healthcare-federated-access-services,GoogleCloudPlatform/healthcare-federated-access-services,GoogleCloudPlatform/healthcare-federated-access-services,GoogleCloudPlatform/healthcare-federated-access-services