Remove Redis config from gitlab-shell
Since gitlab-shell!181 (merged), gitlab-shell no longer can talk to Redis directly. All operations go through the internal API.
Removing this config is useful for several reasons:
- It removes dead code.
- Since the gitlab-shell config is repeatedly parsed with every git action, removing a few lines can improve performance.
- There is a bug in string handling when there are YAML characters included in the Redis password field.