Set showNotification to false does not work in iOS

Hi,
Since we do not want to notify user that the video download is finished, when creating download task, showNotification is set to false in this way:
FlutterDownloader.enqueue(
url: widget.videoUrl,
savedDir: saveDir,
fileName: videoFilename,
**showNotification: false**);
But it does not work.

Steps to reproduce the behavior:
1. Open the app, the video starts downloading
2. Press the home button to make the app run in the background
3. After a while, a notification appears on the top

Seems setting showNotification to false does not work in iOS.

- Device: iPhone 8
- OS: iOS 15.5
- plugin version: 1.7.4

Thanks a lot!

Start by reproducing the issue with FlutterDownloader.enqueue and showNotification: false on iOS, following the listed background-download steps. Confirm whether a notification appears after the app is sent to the background; done means the download completes without showing a notification.

Written by the indexing model from the issue text.