notify: pbs-context: exclude successful prunes in default matcher

PBS sends notifications for all events but successful prune jobs.
There we only care about errors.

This commit adapts the 'default-matcher' to reflect that behavior
as well.

Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>
Tested-by: Maximiliano Sandoval <m.sandoval@proxmox.com>

proxmox-notify/src/context/pbs.rs

@@ -66,8 +66,11 @@ sendmail: mail-to-root
 
 matcher: default-matcher
     mode all
+    invert-match true
+    match-field exact:type=prune
+    match-severity info
     target mail-to-root
-    comment Route all notifications to mail-to-root
+    comment Route everything but successful prune job notifications to mail-to-root
 ";
 
 #[derive(Debug)]