QA: Update exception name inside apidocs

Author: thekid

src/main/php/com/openai/TikTokenFilesIn.class.php

@@ -32,7 +32,7 @@ public function folder(): Folder { return $this->folder; }
    *
    * @param  string $source
    * @throws lang.IllegalArgumentException
-   * @throws io.IOException
+   * @throws io.OperationFailed
    */
   public function tokens($source): iterable {
     $tried= [];