Documentation: BlockSetTypes.md is actually SoundTypes.md

[RonnymonnyTheProgrammer]

I think BlockSetTypes.md contains the text contents of SoundTypes.md: The two are duplicates. It should be easy enough to retrieve what's supposed to be there from an older version, assuming the mistake is recent.

[gigaherz]

:ohno: I don't think this was a mistake of overwriting, but rather that I made a copy with the intention to write that document, and then I never wrote it.