Fixed doc error.

5 jobs for HairlineStroke in 26 minutes and 12 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Prep
passed #5777762
fedora image

00:00:15

 
  Test
passed #5777763
fedora autotools build

00:25:57

passed #5777764
fedora meson build

00:00:55

passed #5777765
docker windows 1809
meson vs2017 amd64

00:03:20

passed #5777766
docker windows 1809
meson vs2017 x86

00:03:23