update comment in :joint-dof definition #145

Job	Run time
catkin	5m 10s
doc	3m 38s
linux (ubuntu:trusty)	3m 59s
linux (ubuntu:xenial)	5m 10s
osx	5m 22s
linux (ubuntu:bionic)	5m 4s
linux (ubuntu:bionic, PQP)	5m 14s
linux (ubuntu:bionic, BULLET)	5m 10s
linux (ubuntu:focal)	5m 40s
linux (debian:stretch)	5m 11s
linux (osrf/ubuntu_armhf:trusty)	31m 5s
linux (osrf/ubuntu_armhf:xenial)	32m 13s
linux (osrf/ubuntu_arm64:xenial)	34m 1s
linux (arm64v8/ubuntu:bionic)	20m 25s
linux (arm64v8/ubuntu:focal)	24m 47s
linux (osrf/debian_arm64:stretch)	35m 43s
	3h 47m 52s

Provide feedback