[Sync EN] Clarify Argon2 memory_cost and time_cost units in password_hash() (#5219)

Commit: `https://github.com/php/doc-en/commit/6cc48aed6f887bdabf09c568f854099f9c74e017`
PR: `https://github.com/php/doc-en/pull/5219`

**Fichiers FR à mettre à jour**
- `reference/password/constants.xml`
- `reference/password/functions/password-hash.xml`
