Remove Redis Command retrieval for Redis Cluster Connections

[mp911de]

With the introduction of Read-Only variants for Geo commands (e.g. GEORADIUSBYMEMBER_RO, GEORADIUS_RO) we started obtaining command details upon connect when using Redis Cluster to ensure that read operations use read commands and utilize replicas.

Since this functionality dates back to Redis 3.2, we should consider removing this step and assume that Read-Only commands are generally available and switch to these.

[mp911de]

Lettuce requires at least Redis 3.2.10 when using Geo Commands. 3.2.0 - 3.2.9 don't ship with _RO commands. See also redis/redis#4084.