BUG/MINOR: quic: Dropped peer transport parameters

BUG/MINOR: quic: Dropped peer transport parameters

The call to quic_dflt_transport_params_cpy() is already first done by
quic_transport_params_init() which is a good thing. But this function was also
called each time we parsed a transport parameters with quic_transport_param_decode(),
re-initializing to default values some of them. The transport parameters concerned
by this bug are the following:
   - max_udp_payload_size
   - ack_delay_exponent
   - max_ack_delay
   - active_connection_id_limit
So, let's remove this call to quic_dflt_transport_params_cpy() which has nothing
to do here!