Change heat_map vis to pr_duration_days instead of time_to_first_response
Change heat_map vis to pr_duration_days instead of time_to_first_response

Signed-off-by: Andrew Brain <19c7abcbd39ccbf7949f6defa6f5b4fd2f58ee38@gmail.com>

OSSHealth/ghdata,OSSHealth/ghdata,OSSHealth/ghdata