Rescue Redis errors from rate limiting

What does this MR do and why?

Every request and Sidekiq job goes through rate limiting. Rescuing the errors prevents taking the site down when the Redis instance is unavailable.

This also prevents thundering retries from Sidekiq and other clients which makes the problem worse when the Redis instance is already saturated.

References

gitlab-com/gl-infra/production#20197 (closed)

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