variant_lists test doesn't exist, don't skip (#496)

Author: Pike

fluent-syntax/test/reference_test.js

@@ -25,7 +25,6 @@ readdir(fixtures, function(err, filenames) {
       // Broken Attributes break the entire Entry right now.
       // https://github.com/projectfluent/fluent.js/issues/237
       "leading_dots.ftl",
-      "variant_lists.ftl"
     ];
 
     for (const filename of ftlnames) {