This change set the Sidekiq retries to 6 for GitHub Stage and
AdvanceStage workers.

These workers can run for a long time, so can be more prone to things
like service interruptions. We'd like them to be more resilient.

The exponential retry backoff will mean 6 retries will introduce nearly
20m total wait time.
https://github.com/sidekiq/sidekiq/wiki/Error-Handling#automatic-job-retry
Any higher retry will hold up an import for too long.

#433326