Fix doc build

Since we increased the precision required in WCS.isEqual, the comparison
below was failing because adjust_coordinates shift the crpix.
5 jobs for master in 15 minutes and 53 seconds (queued for 11 seconds)
Status Job ID Name Coverage
  Test
passed #8404
check-setup

00:02:12

passed #8405
docs

00:05:34

passed #8401
py35

00:06:44

76.0%
passed #8402
py36

00:06:35

76.0%
passed #8403
py37

00:15:52

77.0%