message: Always mute timestamp from screen readers
  The short time is still read out (eg: 15:24), however by ignoring the anchor we prevent the reader from saying the title of the containing span. This prevents readers saying "Wed May 22, 2019 at 15:24 15:24".
  See
diff: @@ -789,7 +789,7 @@ module.exports = withMatrixClient(React.createClass({
  </div>
  { sender }
  <div className="mx_EventTile_line">
  - <a href={permalink} onClick={this.onPermalinkClicked} aria-hidden={muteScreenReader}>
  + <a href={permalink} onClick={this.onPermalinkClicked} aria-hidden={true}>
  { timestamp }
  </a>
  { this._renderE2EPadlock() }
  