nixos/fileSystems: omit comment about swap devices if there are no sw…

…ap devices on the system (#373857)

nixos/modules/tasks/filesystems.nix

@@ -400,7 +400,7 @@ in
         # Filesystems.
         ${makeFstabEntries fileSystems {}}
 
-        # Swap devices.
+        ${lib.optionalString (config.swapDevices != []) "# Swap devices."}
         ${flip concatMapStrings config.swapDevices (sw:
             "${sw.realDevice} none swap ${swapOptions sw}\n"
         )}