Only show notification title in plasmoid if different to app name

Summary: Like we do for the notifications in the plugin already. Passing the title and text separately to the plasmoid could be useful later as well.

Reviewers: KDE Connect, albertvaka

Reviewed By: KDE Connect, albertvaka

Subscribers: KDE Connect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D7457