Fix Method ReflectionProperty::setAccessible() is deprecated since 8.5, as it has no effect

Author: gziolo

tests/phpunit/tests/abilities-api/wpRegisterAbility.php

@@ -456,7 +456,9 @@ public function test_get_existing_ability() {
 		// Reset the Registry, to ensure it's empty before the test.
 		$registry_reflection = new ReflectionClass( WP_Abilities_Registry::class );
 		$instance_prop       = $registry_reflection->getProperty( 'instance' );
-		$instance_prop->setAccessible( true );
+		if ( PHP_VERSION_ID < 80100 ) {
+			$instance_prop->setAccessible( true );
+		}
 		$instance_prop->setValue( null, null );
 
 		$result = wp_get_ability( $name );