listenonly,video-provider,screenshare: remove ICE gathering pre-flight check

...button-html5/imports/ui/components/screenshare/service.js

...-html5/imports/ui/components/video-provider/component.jsx

...uebutton-html5/imports/ui/services/audio-manager/index.js

bigbluebutton-html5/imports/utils/safari-webrtc.js

bigbluebutton-html5/private/config/settings.yml