apt-upgrades: Doesn't work on non-english systems

[koelle25]

Expected behavior

Works on all systems, no matter on which language/locale it is running on.

Actual behavior

Output on non-english systems is just <symbol> / / /.

i3blocks config relevant to blocklet(s)

[apt-upgrades]
...

Output of blocklet(s) when run from command line

<symbol> / / /

Output of any relevant other commands that might help diagnostics

In my case (german system) the relevant output of aptitude is

0 Pakete aktualisiert, 0 zusätzlich installiert, 0 werden entfernt und 0 nicht aktualisiert.

The script is checking for the english output (grep -m1 '^[0-9]\+ packages upgraded,') and so gets an empty value.

I will open a PR fixing this shortly.