While uploading a file the notification should not be dismissable

Summary: BUG: 399983

Test Plan:
Send a big file from Android
The notification can not be dismissed while the file is being transferred

Reviewers: KDE Connect, nicolasfella

Reviewed By: KDE Connect, nicolasfella

Subscribers: nicolasfella, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D16713