upgrade matomo opt out block registration to use API version 3

Author: diosmosis

classes/WpMatomo/OptOut.php

@@ -123,6 +123,7 @@ public function load_block() {
 			'matomo/matomo-opt-out',
 			array(
 				'editor_script' => 'matomo-opt-out',
+				'api_version'   => 3,
 			)
 		);
 	}