Proposed Errata text: Carification to Metadata for <ArtifactResolutionService>

SAMLProf: 
In Section 4.1.6 (Web Browser SSO Profile), at Line 629:

639s/MUST/SHOULD/

New text:
If the request or response message is delivered using
the HTTP Artifact binding, the artifact issuer SHOULD
provide at least one <md:ArtifactResolutionService>
endpoint element in its metadata.