Cache#removeSound()

Removes a sound from the cache.

If any Phaser.Sound objects use the audio file in the cache that you remove with this method, they will
automatically destroy themselves. If you wish to have full control over when Sounds are destroyed then
you must finish your house-keeping and destroy them all yourself first, before calling this method.

Note that this only removes it from the Phaser.Cache. If you still have references to the data elsewhere
then it will persist in memory.