Fix redis diff script breakages
This MR fixes some api breakages and updates the redis-related gems in lieu of gitlab-com/gl-infra/production#17006 (closed).
For running, you would should set the following to reduce start up time.
export REDIS_CLIENT_SLOW_COMMAND_TIMEOUT=10
export REDIS_CLIENT_MAX_STARTUP_SAMPLE=1
bundle exec ruby scripts/redis_diff.rb --migrate --rate=1000 --batch=300 --pool_size=30