Log Message:
libnotify: update to 0.8.1.

Remove gtk3 build dependency, only needed for tests.

New in 0.8.1
============

* Keep version of bindings at 0.7 (#27) [Marco]

New in 0.8.0
============

* Use Desktop Portal Notification when running confined (snap and flatpak)
  Now the library acts like a wrapper in such scenario, with some limited
  capabilities, but this will enforce security and user control over the
  allowed notifications. [Marco]
* notify-send: Handles SIGINT gracefully, closing waiting notification [Marco]
* Use NotifyClosedReason enum as closed reason return value [Marco]
* Bump dependency on GLib 2.38 [Marco]
* Various introspection docs improvements and fixes [Marco]