去掉uniapp button 的边框，默认样式

<button class="useredit-choose-avatar" open-type="chooseAvatar" @chooseavatar="onChooseAvatar"></button>

通过样式修改时无效的，例如：border: none，要通过伪类去掉

.useredit-choose-avatar{
        position: absolute;
        top: 0;
        left: 0;
        right: 0;
        bottom: 0;
        background: transparent;
    }
// 去掉默认边框
.useredit-choose-avatar::after{
        border:none;
    }