Fix: correct to use average and not best case plot.

4 jobs from pure_fork_join in 3 minutes 42 seconds (queued for 11 seconds)
Status Job ID Name Coverage
  Build
passed #3132
build_cmake

00:42

 
  Test
passed #3133
run_tests

00:42

 
  Sanitizer
passed #3135
run_address_sanitizer

01:20

passed #3134
run_thread_sanitizer

00:57