lists: fix name of dmarc mitigation function (team#41981)

service/lists.md

@@ -175,7 +175,7 @@ mitigations set, which will make deliverability problematic. To
 workaround this, run this mitigation in a shell:
 
 ```
-ssh lists-01.torproject.org mailman-wrapper shell -l LISTNAME -r tpa.mm3_tweaks.mitigate
+ssh lists-01.torproject.org mailman-wrapper shell -l LISTNAME -r tpa.mm3_tweaks.mitigate_dmarc
 ```
 
 This is tracked in [issue 41853](https://gitlab.torproject.org/tpo/tpa/team/-/issues/41853).