Default listener location description

[rbxphogen]

Changes

Adds a description for SoundService.DefaultListenerLocation

Checks

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[IgnisRBX]

In cases like this, it would probably be better to move all of this info to the Enum.ListenerLocation page, which this property directly uses and is the sole user of. Could you please migrate each piece of this to that page and then I'll do some touch-ups from there? Thanks!