Disable redis pool because it's already implemented

What does this MR do and why?

Let's explicitly disable the pool because we already wrapping the connection into pool:

• Gitlab::Redis::Wrapper
• Rails wrapper

With Rails 7.0 it doesn't wrap it anyway, but with Rails 7.1 we receive an error because the connection is wrapped twice.

A better option is to correctly propagate pool options to Rails instead of wrapping our Redis clients into connection pools. However, it will be more efficient to do it after we upgrade to Rails 7.1 because the format has changed:

• Rails 7.0.6
• Rails (main)