Refactor part of the mean_response_times_for_PR endpoint
Refactor part of the mean_response_times_for_PR endpoint

Signed-off-by: Andrew Brain <c826a0325a4019c4e3a943765451239be53ee3a6@users.noreply.github.com>

OSSHealth/ghdata,OSSHealth/ghdata,OSSHealth/ghdata