notifications: Correctly display the file in jobs

Summary:
For url with parameter like audiocd:/1.wav?device=/dev/sr0, the filename
displayed in notifications applet is not correct ("sr0") instead of 1.wav.
This commit try to remove the query string before extract the last path
component.

Test Plan: Manually with audiocd-kio

Reviewers: mart, davidedmundson

Reviewed By: davidedmundson

Subscribers: davidedmundson, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D4879