system-helper: Make uninstall auth message friendlier
system-helper: Make uninstall auth message friendlier

Currently when a polkit prompt is created for an app uninstallation, the
message is something like "Authentication is required to uninstall
app/us.zoom.Zoom/x86_64/stable" which is not very friendly for
non-technical users. Change it to "Authentication is required to
uninstall Zoom".

For many of the other polkit actions used by the system-helper, we just
say "software" rather than specifying the app/runtime, since we use the
authorization from one action for others via imply annotations, so the
user is really authorizing several things at once in some cases. In the
case of app-uninstall actions, the only implied action is
runtime-uninstall, and runtimes aren't something users should generally
have to worry about anyway, so it seems alright to specify the app. I
presume that was why commit 21f845c1a didn't remove the ref from the
app-uninstall action message.

flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak