Declare return type for data_got_mod_rewrite() in unit test.

Author: Paul Bearne

tests/phpunit/tests/admin/includes/misc/gotModRewrite.php

@@ -56,7 +56,7 @@ public function test_got_mod_rewrite( $expected, $apache_loaded, $filter_value =
 	 *     filter_value:  bool|null,
 	 * }>
 	 */
-	public function data_got_mod_rewrite() {
+	public function data_got_mod_rewrite(): array {
 		return array(
 			'Default behavior (should match filter or internal check)' => array(
 				'expected'      => true,