[ticket/17176] Fix some PHP 8.x deprecations and clean up test code

PHPBB3-17176

tests/controller/controller_test.php

@@ -21,6 +21,9 @@ use Symfony\Component\DependencyInjection\Loader\YamlFileLoader;
 
 class phpbb_controller_controller_test extends phpbb_test_case
 {
+	/** @var phpbb_mock_extension_manager */
+	protected $extension_manager;
+
 	protected function setUp(): void
 	{
 		$this->extension_manager = new phpbb_mock_extension_manager(