tls-test: Update error message to match new boringssl behavior

Introduced in 58d56f4c5 ("Enable TLS 1.3 by default").

c++/src/kj/compat/tls-test.c++

@@ -531,7 +531,7 @@ KJ_TEST("TLS client certificate verification") {
         serverPromise.wait(test.io.waitScope));
     KJ_EXPECT_THROW_MESSAGE(
         SSL_MESSAGE("alert",  // "alert handshake failure" or "alert certificate required"
-                    "SSLV3_ALERT_HANDSHAKE_FAILURE"),
+                    "TLSV1_CERTIFICATE_REQUIRED"),
         clientPromise.wait(test.io.waitScope));
   }