fix: remove scan duration hint text from auto-scan page

miniprogram/pages/auto-scan/auto-scan.wxml

@@ -9,7 +9,6 @@
     <!-- 待开始 -->
     <view wx:if="{{phase === 'ready'}}">
       <view class="scan-hint">设备已佩戴，点击下方按钮开始智能检测</view>
-      <view class="scan-hint sub-hint">检测过程约需 2 分钟，请保持设备贴合</view>
       <button class="btn-primary mt-30" bindtap="onStartScan">开始检测</button>
     </view>