Change method visibility to protected...

... because the parent function is also `protected`.

Author: jrauh01

src/Widget/ButtonLink.php

@@ -41,7 +41,7 @@ public function createHrefAttribute(): ?Attribute
         return parent::createHrefAttribute();
     }
 
-    public function assemble(): void
+    protected function assemble(): void
     {
         parent::assemble();