The "Update SBOM file" section of CONTRIBUTING.md only mentions Docker as a prerequisite for scripts/update-sbom.sh.

Since PR #2039, the script pulls the Silkbomb image from the DevProd ECR registry instead of Artifactory, which adds requirements that are not documented:
* AWS CLI installed and an AWS SSO profile for account 901841024863
* Membership in the devprod-platforms-ecr-users Okta group, see [https://docs.devprod.prod.corp.mongodb.com/devprod-platforms-ecr#from-your-laptop]
* The profile name can be overridden with the DEVPROD_PLATFORMS_ECR_AWS_PROFILE environment variable; the default is ECRScopedAccess-901841024863
* Submodules must be checked out, since the script reads src/libmongoc/VERSION_CURRENT

Without an ECR login, the script fails with "The config profile (ECRScopedAccess-901841024863) could not be found" followed by "password is empty".

Update CONTRIBUTING.md to list these prerequisites.