Mark MediaStreamTrack: onmute as standard (#5400)
Mark MediaStreamTrack: onmute as standard (#5400)

https://w3c.github.io/mediacapture-main/#dom-mediastreamtrack-onmute
is the standard that normatively defines MediaStreamTrack: onmute.
mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data