[Sync EN] Phar::setStub: Add a description of the `$length` parameter (#5592)

[github-actions]

Commit: https://github.com/php/doc-en/commit/d7056bd0948e3dd9316708247933026bd3d560b1
PR: https://github.com/php/doc-en/pull/5592

Fichiers FR à mettre à jour

• reference/phar/Phar/setStub.xml
• reference/phar/PharData/setStub.xml