Adapt api.RTCDTMFSender.ontonechange to new events structure (#15188)
Adapt api.RTCDTMFSender.ontonechange to new events structure (#15188)

This PR adapts the tonechange event of the RTCDTMFSender API to conform to the new events structure.
chrisdavidmills/browser-compat-data,mdn/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data