Remove Sidekiq Cluster option from Helm charts

In 12.10, via #198 (closed), we added support for Sidekiq Cluster in our Helm charts.

In 13.0, via gitlab-org/charts/gitlab#1989 (closed), we are making it the default, but still allowing people to disable cluster if they want. For the Helm charts, the main difference is in how queues and negateQueues are configured, as described in that issue.

In 14.0, we'll remove the cluster option:

1. We'll always use sidekiq-cluster in https://gitlab.com/gitlab-org/build/CNG/-/blob/master/gitlab-sidekiq/scripts/process-wrapper.
2. We'll only support strings for queues and negateQueues.
3. We can remove https://gitlab.com/gitlab-org/charts/gitlab/-/blob/master/charts/gitlab/charts/sidekiq/templates/configmap-queue.yaml and the associated code entirely.
4. We'll need to add deprecations: https://docs.gitlab.com/charts/architecture/decisions.html#breaking-changes-via-deprecation