Update Sidekiq dev docs: describe "renaming the worker"
Was extracted from this discussion: #439738 (comment 1776452247)
Our Sidekiq docs does not cover the case when you need to rename the worker and queue: https://gitlab.com/gitlab-org/gitlab/blob/b40fab0ecd4e1078067479c9d2cad355efe4cdfe/doc/development/sidekiq/compatibility_across_updates.md#L19
We should improve the docs.