Fixes RedisCluster constants deprecation in PHPRedis 6.

[lucasromanojf]

When deploying a project which uses Tenancy for Laravel to Laravel Vapor using PHP 8.3 runtime (which uses PHPRedis 6) and a Redis cluster, the following error occurs:

Undefined constant RedisCluster::OPT_PREFIX

As detailed in this Laravel merged PR:

laravel/framework#48362

The PHPRedis library removed RedisCluster:: constants since 6.0.0. (...)

The author of PHPREDIS recommends not using the constants of RedisCluster anymore but using the constants in Redis instead (...)

This PR changes the use of $client:: (which can lead to the mentioned error when working with PHPRedis 6 and a Redis cluster) for constants to \Redis::.

Also, as stated in the Laravel PR mentioned above:

This is backward compatible since the underlying values of these constants are the same, so it will still work for older phpredis versions

[stancl]

Thanks for the PR! Implemented this in v4 the exact same way.

[lucasromanojf]

Thanks for merging it so fast!