Say on the progress bar that this is an update running

The headline read "Paketquellen" over KDE's own "0 von 123 Elementen" -
two nouns and a count, with nothing anywhere saying that the machine was
updating itself. Nobody goes looking for this entry; it turns up beside
whatever they were doing, so it has to explain itself in one line.

Each step now says so outright: "Systempakete werden aktualisiert",
"Flatpak-Programme werden aktualisiert", and so on.

The count line underneath belongs to Plasma, which only counts in bytes,
files, dirs or items - "Paketen" is not on offer, so "Elementen" stays,
now under a headline that says what is being counted.

src/lib/pkg_aur.sh

@@ -126,7 +126,7 @@ cau_aur_update() {
 
 	cau_aur_ready || return 0
 
-	cau_progress_step aur "AUR packages"
+	cau_progress_step aur "Updating AUR packages"
 
 	pending="$(cau_aur_pending)"
 	if (( pending == 0 )); then