Improve disabled_properties option spec for PropertySpelling
Improve disabled_properties option spec for PropertySpelling

The previous spec was a bit odd--`made-up-property` wasn't a
property name anyway, so a lint would be reported regardless of whether
it was blacklisted (it just so happens that the implementation wouldn't
allow that, but this change makes the spec a little safer).

cih/scss-lint,teoljungberg/scss-lint