ARC signing instead of DKIM signing.

conf/modules.d/arc.conf

@@ -45,7 +45,7 @@ arc {
   symbol_sign = "ARC_SIGNED";
   # Whether to fallback to global config
   try_fallback = true;
-  # Domain to use for DKIM signing: can be "header" or "envelope"
+  # Domain to use for ARC signing: can be "header" or "envelope"
   use_domain = "header";
   # Whether to normalise domains to eSLD
   use_esld = true;