fix open param type

Author: Philippe Khill

src/NestedForm.php

@@ -2,6 +2,7 @@
 
 namespace Yassi\NestedForm;
 
+use function GuzzleHttp\json_encode;
 use Illuminate\Support\Facades\Route;
 use Illuminate\Support\Str;
 use Illuminate\Validation\ValidationException;
@@ -20,9 +21,8 @@
 use Laravel\Nova\Http\Requests\NovaRequest;
 use Laravel\Nova\Http\Requests\UpdateResourceRequest;
 use Laravel\Nova\Nova;
-use Laravel\Nova\Panel;
 
-use function GuzzleHttp\json_encode;
+use Laravel\Nova\Panel;
 
 class NestedForm extends Field
 {
@@ -249,7 +249,7 @@ public function heading(string $heading)
      * 
      * @param boolean $opened
      */
-    public function open(boolean $opened)
+    public function open(bool $opened)
     {
         $this->opened = $opened;