[Rspamd] Forced action add header seems to be broken atm, switching to rewrite subject until fixed

data/conf/rspamd/local.d/force_actions.conf

@@ -1,6 +1,6 @@
 rules {
   WHITELIST_FORWARDING_HOST_NO_REJECT {
-    action = "add header";
+    action = "rewrite subject";
     expression = "WHITELISTED_FWD_HOST";
     require_action = ["reject"];
   }