[iOS] 使用 SnapKit 时 view 向下滑出屏幕的写

• 简单动画

    /// 向下滑出日历
    private func hideCalendarViewWithAnimation() {
        UIView.animate(withDuration: 0.33, animations: {
            self.viewContain.snp.updateConstraints({ (make) in
                make.bottom.equalTo(self.view).offset(self.heightCalendar)
            })
            self.view.layoutIfNeeded()
        }) { (_) in
            self.viewContain.removeFromSuperview()
        }
    }