Fix PHP 8.4 implicit nullable parameter deprecations in Predis library

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.

plugins/cache-redis/Predis/Protocol/Text/CompositeProtocolProcessor.php

@@ -41,8 +41,8 @@ class CompositeProtocolProcessor implements ProtocolProcessorInterface
      * @param ResponseReaderInterface    $reader     Response reader.
      */
     public function __construct(
-        RequestSerializerInterface $serializer = null,
-        ResponseReaderInterface $reader = null
+        ?RequestSerializerInterface $serializer = null,
+        ?ResponseReaderInterface $reader = null
     ) {
         $this->setRequestSerializer($serializer ?: new RequestSerializer());
         $this->setResponseReader($reader ?: new ResponseReader());