fix return type of to_object of final event transformers

includes/activitypub/transformer/class-events-manager.php

@@ -264,7 +264,7 @@ final class Events_Manager extends Event_Transformer {
 	 *
 	 * @return Activitypub\Activity\Event
 	 */
-	public function to_object() {
+	public function to_object(): Event {
 		$this->em_event     = new EM_Event( $this->wp_object->ID, 'post_id' );
 		$activitypub_object = new Event();
 

includes/activitypub/transformer/class-gatherpress.php

@@ -199,7 +199,7 @@ final class GatherPress extends Event {
 	 *
 	 * @return Activitypub\Activity\Event
 	 */
-	public function to_object() {
+	public function to_object(): Event_Object {
 		$activitypub_object = parent::to_object();
 
 		return $activitypub_object;

includes/activitypub/transformer/class-the-events-calendar.php

@@ -14,6 +14,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 
 use Activitypub_Event_Extensions\Activitypub\Transformer\Event;
 use Activitypub\Activity\Extended_Object\Place;
+use Activitypub\Activity\Extended_Object\Event as Event_Object;
 use WP_Error;
 use WP_Post;
 
@@ -194,7 +195,7 @@ final class The_Events_Calendar extends Event {
 	 *
 	 * @return Event_Object
 	 */
-	public function to_object() {
+	public function to_object(): Event_Object {
 		$activitypub_object = parent::to_object();
 
 		return $activitypub_object;