[handler] Improve text if a file is shared

Summary:
The handler allows to easily integrate file sharing into various file managers. Make it appear nicer by removing the scheme and using a different wording when sending
files

Test Plan:

Reviewers: KDE Connect, apol

Reviewed By: KDE Connect, apol

Subscribers: apol, kdeconnect

Tags: KDE Connect

Differential Revision: https://phabricator.kde.org/D16605