[mediacapture-screen-share] Audio is said to be optional but there's one place that implies that it is not (#101)

henbos has just created a new issue for https://github.com/w3c/mediacapture-screen-share:

== Audio is said to be optional but there's one place that implies that it is not ==
The spec says audio is optional (e.g. [here](https://w3c.github.io/mediacapture-screen-share/#capturing-logical-or-visible-display-surfaces and [here](https://w3c.github.io/mediacapture-screen-share/#dom-mediadevices-getdisplaymedia)), which is very much intentional, but if you follow the getDisplayMedia() steps we find a contradiction:

> The provided media MUST include precisely one track of each media type in requestedMediaTypes. The devices chosen MUST be the ones determined by the user. Once selected, the source of a MediaStreamTrack MUST NOT change.

We should clarify that in the cause of audio the audio track must not be included.

Please view or discuss this issue at https://github.com/w3c/mediacapture-screen-share/issues/101 using your GitHub account