test: have TestOptionalDisclosure also compare issuance time (cf. 82a4ad47)

internal/sessiontest/requestor_test.go

@@ -251,6 +251,7 @@ func TestOptionalDisclosure(t *testing.T) {
 				Value:        map[string]string{"": radboud, "en": radboud, "nl": radboud},
 				Identifier:   irma.NewAttributeTypeIdentifier("irma-demo.RU.studentCard.university"),
 				Status:       irma.AttributeProofStatusPresent,
+				IssuanceTime: irma.Timestamp(client.Attributes(university.CredentialTypeIdentifier(), 0).SigningDate()),
 			},
 		},
 		{},