The ImageMagick and RHEL related conditionals were dropped in commit
d0508a7, but they have to stay, because only RHEL 7 had ImageMagick and
not any newer versions of RHEL. Currently it's only autotrace that is
pulling ImageMagick into ELN/RHEL 10.
Also update the github-#70 test so it's expected to fail when compiled
without ImageMagick support (due to lack of XPM support).
