remove tentative return annotation

Author: shyim

ext/zip/php_zip.stub.php

@@ -641,7 +641,6 @@ class ZipArchive implements Countable
     /** @tentative-return-type */
     public function open(string $filename, int $flags = 0): bool|int {}
 
-    /** @tentative-return-type */
     public function openBuffer(string $data): void {}
 
     /**