UtteranceQueue implementAsSkeleton is an anti-pattern

[zepumph]

While working on #17, I'm pretty sure that we could get rid of this confusing implementation detail in UtteranceQueue (a remnant of baseline API files for PhET-iO). I don't think there is anything checking the runtime against what is expected to be in it. This shouldn't even be an API change, since the sims being published with description are the only ones that should have an UtteranceQueue.

[zepumph]

@jessegreenberg mentioned that we can't do this until there aren't any more usages that use the global pattern like

phet.joist.sim.display.utteranceQueue, because in some common code that may be called when not in a description-supported runtime.