message: Add missing `key` to `ReplyInThreadButton` as used in `MessageActionBar`
diff: @@ -384,7 +384,7 @@ export default class MessageActionBar extends React.PureComponent<IMessageAction
  key="cancel"
  />;
  - const threadTooltipButton = <ReplyInThreadButton mxEvent={this.props.mxEvent} />;
  + const threadTooltipButton = <ReplyInThreadButton mxEvent={this.props.mxEvent} key="reply_thread" />;
  // We show a different toolbar for failed events, so detect that first.
  const mxEvent = this.props.mxEvent;
  