ca: simplify code a bit

Co-authored-by: Luke Valenta <[email protected]>

ca/ca.go

@@ -376,7 +376,7 @@ func Open(path string) (*Handle, error) {
 		return nil, fmt.Errorf("parsing %s: %w", h.skPath(), err)
 	}
 	switch h.params.EvidencePolicy {
-	case mtc.EmptyEvidencePolicyType:
+	case mtc.EmptyEvidencePolicyType, mtc.UmbilicalEvidencePolicyType:
 	case mtc.UmbilicalEvidencePolicyType:
 	default:
 		return nil, fmt.Errorf("unknown evidence policy: %d", h.params.EvidencePolicy)