`hasDefault` param doesn't need to be set if default variant is found

[Pike]

Found this when comparing the 0.8 branches of python and js, hasDefault = true is useless in

fluent.js/fluent-syntax/src/parser.js

Line 336 in 6edf276

hasDefault = true;

?

[stasm]

Fixed by #325 and merged into master in #303.