sway: unfail units before starting session target

Sometimes services can fail. Failed services will generally not be
restarted by systemd. To start previously failed services we can
just reset their failed state before starting our session target.

GNOME and Plasma do the same thing.

See: https://github.com/alebastr/sway-systemd/pull/11

modules/services/window-managers/i3-sway/sway.nix

@@ -412,6 +412,7 @@ in {
       extraCommands = mkOption {
         type = types.listOf types.str;
         default = [
+          "systemctl --user reset-failed"
           "systemctl --user start sway-session.target"
           "swaymsg -mt subscribe '[]' || true"
           "systemctl --user stop sway-session.target"