tris: enable TLS 1.3 for tris-localserver again.

The default version (TLS 1.2) is no longer overridden with TLS 1.3 so
the server must explicitly set it.

Fixes: ("crypto/tls: allow client to pick TLS 1.3, do not enable it by default.")

_dev/tris-localserver/server.go

@@ -51,6 +51,7 @@ func startServer(addr string, rsa, offer0RTT, accept0RTT bool) {
 				time.Sleep(500 * time.Millisecond)
 				return nil, nil
 			},
+			MaxVersion: tls.VersionTLS13,
 		},
 	}
 	log.Fatal(s.ListenAndServeTLS("", ""))