[Form] use never return type in form events

Author: HeahDude

Event/PostSetDataEvent.php

@@ -22,7 +22,7 @@
  */
 final class PostSetDataEvent extends FormEvent
 {
-    public function setData(mixed $data): void
+    public function setData(mixed $data): never
     {
         throw new BadMethodCallException('Form data cannot be changed during "form.post_set_data", you should use "form.pre_set_data" instead.');
     }

Event/PostSubmitEvent.php

@@ -22,7 +22,7 @@
  */
 final class PostSubmitEvent extends FormEvent
 {
-    public function setData(mixed $data): void
+    public function setData(mixed $data): never
     {
         throw new BadMethodCallException('Form data cannot be changed during "form.post_submit", you should use "form.pre_submit" or "form.submit" instead.');
     }