build: Ignore error from pkill on apt upgrade (fixes #7628) (#7629)

script/deb-post-inst.template

@@ -10,5 +10,5 @@ fi
 if [ $has_systemd -eq 0 ] && [ -n "$(systemctl list-units --plain --no-legend {{.Service}})" ]; then
     deb-systemd-invoke try-restart "{{.Service}}"
 else
-    pkill -HUP -x {{.Command}}
+    pkill -HUP -x {{.Command}} || :
 fi