revert: switch back to ipv4 for ip-update service

Signed-off-by: Reputable2722 <153411261+Reputable2772@users.noreply.github.com>

Author: Reputable2772

Users/WickedWizard/Programs/Selfhosted/ip-update.nix

@@ -24,7 +24,7 @@
           --data-urlencode "token=$secret" \
           --data-urlencode "domains=$DOMAIN" \
           --data-urlencode "verbose=true" \
-          --data-urlencode "ipv6=$ip6"
+          --data-urlencode "ip=$ip"
       '';
     };
   };