Add 14.0 deprecation notices to Sidekiq cluster / queues docs

What does this MR do?

In 14.0 (or later), we'll remove the cluster option for the Sidekiq chart. This has a downstream effect that means that you can no longer pass an array to queues or negateQueues. This MR attempts to clarify that.

Related issues

Release post announcement: gitlab-com/www-gitlab-com!76595 (merged)

Overall epic: gitlab-com/gl-infra&198 (closed)

Author's checklist (required)

• Follow the Documentation Guidelines and Style Guide.
• If you have developer access or higher (for example, GitLab team members or Core Team members)
  • Apply the documentation label, plus:
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  • Assign the designated Technical Writer.

Do not add the ~"feature", frontend, backend, ~"bug", or database labels if you are only updating documentation. These labels will cause the MR to be added to code verification QA issues.

When applicable:

• Add GitLab's version history note(s).

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.
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  • Add twdoing when starting work on the MR.
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2. Ensure a release milestone is set.
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