Tweak "bad APIs" wording

On the main page it says:
> Most metrics attempt to capture a count of bad APIs.

Can we clarify this to "potentially problematic" instead of "bad"? There are lots of examples where something isn't necessarily bad. Eg. Firefox ships some APIs defined in REC standards agreed upon by all major vendors but which none of the other browsers have caught up to yet. Such cases do represent bugs in the platform somewhere, but we don't want to imply that Firefox is "bad" in that case.