Merge branch 'tchu-update-sidekiq-failure-handling-docs' into 'master'

Update Sidekiq failure handling docs

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/159430



Merged-by: Peter Leitzen <pleitzen@gitlab.com>
Approved-by: Peter Leitzen <pleitzen@gitlab.com>
Co-authored-by: Terri Chu <tchu@gitlab.com>

doc/development/sidekiq/index.md

@@ -132,12 +132,16 @@ If you need to perform an action when a job fails after all of its retry attempt
 
 ```ruby
 sidekiq_retries_exhausted do |msg, ex|
-  project = Project.find(msg['args'].first)
+  project = Project.find_by_id(msg['args'].first)
+  return unless project
+
   project.perform_a_rollback # handle the permanent failure
 end
 
 def perform(project_id)
-  project = Project.find(project_id)
+  project = Project.find_by_id(project_id)
+  return unless project
+
   project.some_action # throws an exception
 end
 ```