Document retry_job and retry_pipeline commands

Why is this change being made?

We have added two new commands to triage-ops: https://gitlab.com/gitlab-org/quality/triage-ops/-/blob/master/triage/processor/gitlab_internal_commands/command_retry_pipeline_or_job.rb:

• retry_job: retrying a failed job
• retry_pipeine: retrying all failed jobs for a pipeline

This MR documents the automation details.

Re: Only maintainer are allowed to retry jobs in Gi... (gitlab-org/quality/engineering-productivity/team#258 - closed)

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
  • The when to get approval handbook section explains the workflow in more detail
• If the changes affect team members, or warrant an announcement in another way, please consider posting an update in #whats-happening-at-gitlab linking to this MR
  • If this is a change that directly impacts the majority of global team members, it should be a candidate for #company-fyi. Please work with internal communications and check the handbook for examples.

---