Voice messages contain a `waveform` key in `org.matrix.msc1767.audio`, which is not specced

[Half-Shot]

I found this while trying to report another bug, but since I don't have a spec to follow it's difficult to tell what the format of waveform is meant to be.

MSC1767

[Half-Shot]

Ah, it appears to be matrix-org/matrix-spec-proposals#3246. Since that MSC doesn't include a prefix, I guess this is fine.

[turt2live]

Ftr, lack of prefix in an MSC does not mean someone can use it without a prefix. In this case, the property is under an all-new prefixed key and thus doesn't need overspecification.