The `attempt_threshold` option in `sentry-sidekiq` will silently drop jobs with low retry count

[marcboquet]

Problem Statement

The attempt_threshold (added in #2503) has a bug when a job's retry option is lower than its attempt_threshold (e.g. retry: 1 with attempt_threshold: 3).

In those cases the error handler skipped every attempt and the job was silently dropped.

Solution Brainstorm

#2940

[linear-code]

RUBY-176