Mark SpeechSynthesisUtterance.p.onboundary partial (#7385)
Mark SpeechSynthesisUtterance.p.onboundary partial (#7385)

This change marks SpeechSynthesisUtterance.p.onboundary and the
boundary event partially supported in Chrome Android, due to the fact
the event doesn’t fire expected. See https://crbug.com/1122143.

Fixes https://github.com/mdn/browser-compat-data/issues/6772

Co-authored-by: Daniel D. Beck <3d0f3b9ddcacec30c4008c5e030e6c13a478cb4f@ddbeck.com>
mdn/browser-compat-data,chrisdavidmills/browser-compat-data,mdn/browser-compat-data,chrisdavidmills/browser-compat-data