message: remove unnecessary mobileViewPlaceholder
diff: @@ -34,7 +34,6 @@ interface Props extends HTMLAttributes<HTMLDivElement>, HasPlatform, HasFormLabe
  dayPlaceholder?: string;
  monthPlaceholder?: string;
  yearPlaceholder?: string;
  - mobileViewPlaceholder?: string;
  onDateChange?: (value: string) => void;
  }
  @@ -197,7 +196,7 @@ class DatePicker extends Component<Props, State> {
  }
  get mobileView() {
  - const { top, name, min, max, mobileViewPlaceholder } = this.props;
  + const { top, name, min, max } = this.props;
  const { day, month, year } = this.state;
  if (day && month && year) {
  @@ -219,7 +218,6 @@ class DatePicker extends Component<Props, State> {
  top={top}
  name={name}
  type="date"
  - placeholder={mobileViewPlaceholder}
  onChange={this.onStringChange}
  min={min}
  max={max}
  