[h2olog] Fix parameter position in example usage
[h2olog] Fix parameter position in example usage

`-p` should appear right in front of a process ID.

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