nixos/sudo: Drop the sudoers comment for extraRules

All rules are now handled through `extraRules`,
and it is never empty so `optionalString` isn't needed either.

nixos/modules/security/sudo.nix

@@ -240,9 +240,7 @@ in
         # Keep SSH_AUTH_SOCK so that pam_ssh_agent_auth.so can do its magic.
         Defaults env_keep+=SSH_AUTH_SOCK
       '')
-      (optionalString (cfg.extraRules != []) ''
-        # extraRules
-        ${concatStringsSep "\n" (
+      (concatStringsSep "\n" (
         lists.flatten (
           map (
             rule: optionals (length rule.commands != 0) [
@@ -251,8 +249,7 @@ in
             ]
           ) cfg.extraRules
         )
-        )}
-      '')
+      ) + "\n")
       (optionalString (cfg.extraConfig != "") ''
         # extraConfig
         ${cfg.extraConfig}