set matchGoodness to lowest number for prefix matches

Fix for issue #3534 (https://github.com/adobe/brackets/issues/3534). The matchGoodness score for hints that match the prefix of a hint have a different value based on the length of the hint. For code hints, the length of the hint should not matter so this fix sets them to be all the same. When all the prefix matches have the same matchGoodness score, the secondary sorts for scope depth and builtin vs. not-builtin can kick in.