Use the right variable in this loop

This was broken accidentally in b2a4f4f.

Author: PeterJCLaw

django_lightweight_queue/management/commands/queue_configuration.py

@@ -54,4 +54,4 @@ def handle(self, **options: Any) -> None:
                 'timeout',
                 'sigkill_on_stop',
             ):
-                print("{:20s}: {}".format(key, config.get(k, '-')))
+                print("{:20s}: {}".format(key, config.get(key, '-')))