This change drops the SiteBoundCredential interface in favor of a CredentialUserData mixin. This change was introduced in the Credential Manager API specification with commit a43865bd8aa9842dbc8d8e688d5668c087677eac (https://github.com/w3c/webappsec-credential-management/commit/a43865bd8aa9842dbc8d8e688d5668c087677eac).
Docs: https://developer.mozilla.org/en-US/docs/Web/API/Credential_Management_API