ext/standard: Transform tentative return types into proper types for Directory class

This class is now final

Author: Girgias

ext/standard/dir.stub.php

@@ -99,19 +99,16 @@ final class Directory
     public readonly mixed $handle;
 
     /**
-     * @tentative-return-type
      * @implementation-alias closedir
      */
     public function close(): void {}
 
     /**
-     * @tentative-return-type
      * @implementation-alias rewinddir
      */
     public function rewind(): void {}
 
     /**
-     * @tentative-return-type
      * @implementation-alias readdir
      */
     public function read(): string|false {}