revert: trailing comma in clipboard_button.dart

Author: EchoEllet

lib/src/toolbar/buttons/clipboard_button.dart

@@ -29,9 +29,7 @@ class ClipboardMonitor {
 
     if (add) {
       _timer = Timer.periodic(
-        const Duration(seconds: 1),
-        (timer) => _update(listener),
-      );
+        const Duration(seconds: 1), (timer) => _update(listener));
     } else {
       _timer?.cancel();
     }