systemd: fix install from backports

systemd/init.sls

 systemd_pkgs:
   pkg.latest:
-{%- if grains['osfinger'] == "Debian-9" %}
-    - fromrepo: stretch-backports
-    - require:
-      - pkgrepo: stretch-backports
-{%- elif grains['osfinger'] == "Debian-10" %}
-    - fromrepo: buster-backports
-    - require:
-      - pkgrepo: buster-backports
-{%- elif grains['osfinger'] == "Debian-11" %}
-    - fromrepo: bullseye-backports
-    - require:
-      - pkgrepo: bullseye-backports
-{%- elif grains['osfinger'] == "Debian-12" %}
-    - fromrepo: bookworm-backports
-    - require:
-      - pkgrepo: bookworm-backports
+{%- if grains['osmajorrelease'] >= "9" and grains['osmajorrelease'] <= "12" %}
+    - fromrepo: {{ oscodename }}-backports
 {%- endif %}
     - pkgs:
       - systemd