Disables album art download on metered connections (e.g. 4G)

Summary: Won't typically be a problem (you're usually connected via wifi with KDE Connect anyway), but shouldn't hurt.

Test Plan: Works with the bluetooth backend on 4G (i.e. no album art is downloaded). Still downloads album art otherwise, as expected.

Reviewers: KDE Connect, nicolasfella

Reviewed By: KDE Connect, nicolasfella

Subscribers: KDE Connect

Differential Revision: https://phabricator.kde.org/D11682