client: Use conservative default UDP payload size
Client should use conservative default UDP payload size in the
presence of VPN which reduces effective MTU.
namespace ngtcp2 {
constexpr size_t server_max_udp_payload_size = 1472;
-constexpr size_t client_max_udp_payload_size = 1362;
+constexpr size_t client_max_udp_payload_size = NGTCP2_MAX_UDP_PAYLOAD_SIZE;
enum network_error {
NETWORK_ERR_OK = 0,
