fix `quicly_num_streams_by_group` referring to incorrect stream group, by uisng same logic as quicly.c
fix `quicly_num_streams_by_group` referring to incorrect stream group, by uisng same logic as quicly.c

h2o/h2o,yannick/h2o,devnexen/h2o,devnexen/h2o,h2o/h2o,h2o/h2o,yannick/h2o,yannick/h2o,h2o/h2o,h2o/h2o,devnexen/h2o,yannick/h2o,devnexen/h2o,devnexen/h2o,h2o/h2o,yannick/h2o,devnexen/h2o,h2o/h2o,devnexen/h2o,yannick/h2o,yannick/h2o,devnexen/h2o,h2o/h2o,devnexen/h2o,yannick/h2o,yannick/h2o,h2o/h2o