We still count on Bug 1356124 to fix font-variant-alternates longhand, so we
can get font-variant shorthand work properly.

Some comments about Bug 1356124 have been removed, since this shorthand code
should just work once we fix Bug 1356124.

From gecko bug: Bug 1356134 (https://bugzilla.mozilla.org/show_bug.cgi?id=1356134)