[PasswordHasher] Fix documentation link

Author: chalasr

README.md

@@ -33,7 +33,7 @@ $passwordHasher->verify($hash, 'plain'); // returns true (valid)
 Resources
 ---------
 
- * [Documentation](https://symfony.com/doc/current/password-hasher.html)
+ * [Documentation](https://symfony.com/doc/current/security.html#c-hashing-passwords)
  * [Contributing](https://symfony.com/doc/current/contributing/index.html)
  * [Report issues](https://github.com/symfony/symfony/issues) and
    [send Pull Requests](https://github.com/symfony/symfony/pulls)