Make retry an integer in Sidekiq logs

What does this MR do?

https://github.com/mperham/sidekiq/wiki/Error-Handling#configuration says that retry: false is not exactly equivalent to retry: 0 - it's more like retry: 0, dead: false.

For logging, those cases are basically the same, though, and making this always an integer prevents mapping errors. See gitlab-com/gl-infra/production#2090 (closed) for an issue that was caused by this.