fix: H5 DownloadTask 支持 offProgressUpdate

src/platforms/h5/service/api/network/download-file.js

@@ -18,6 +18,12 @@ class DownloadTask {
     }
     this._callbacks.push(callback)
   }
+  offProgressUpdate (callback) {
+    const index = this._callbacks.indexOf(callback)
+    if (index >= 0) {
+      this._callbacks.splice(index, 1)
+    }
+  }
   /**
    * 停止任务
    */