Remove FF ci_remove_update_retried_from_process_pipeline

What does this MR do and why?

This also removes redundant codes. Most importantly, Ci::ProcessPipelineService#update_retried 🚀

• This FF was enabled on GitLab.com in 14.2: #321630 (comment 670052611)
• This FF was enabled by default in 14.3: #321630 (comment 678578995)

• Rollout issue: #321630 (closed)
• Related issue: #326791 (closed)
• Introduced in: !54300 (merged)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.