PHP 8.4 deprecates implicitly nullable parameter types. Parameters with a default value of `null` must now be explicitly marked as nullable (e.g., `?Type $var = null`).
This change updates the vendored `Predis` library in `plugins/cache-redis/` to comply with this requirement. It scans for function signatures like `Type $var = null` and updates them to `?Type $var = null`. This ensures compatibility with PHP 8.4 and PHP 8.5 while maintaining backward compatibility.
Affected files include `Predis` interfaces, connection classes, and command definitions.
Also updated PHPDoc `@method` annotations to reflect nullable types.
