Handbook: Add MR review app restarts for blog post troubleshooting

Why is this change being made?

Review apps and their deployments to environments are stopped after a defined interval, for cost saving reasons. While we work on other solutions to make this more convenient for blog post reviews, this MR adds a troubleshooting entry to the handbook. It may also help with future troubleshooting when review apps are stopped for some reason.

I normally don't add a screenshot to the handbook but in this specific case, explaining the CI/CD icons to click in text is nearly impossible.

• MR report
• Handbook escalation slack
• Release post slack

Thanks @marcel.amirault for the hint!

cc @skassabian @erica @fseifoddini @jeanduplessis

Author Checklist

• Provided a concise title for the MR
• Added a description to this MR explaining the reasons for the proposed change, per say-why-not-just-what
• Assign this change to the correct DRI
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to your manager.
  • 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.
  • If the changes relate to any part of the project other than updates to content and/or data files please make sure to ping @gl-static-site-editor in a comment for a review and merge. For example changes to .gitlab-ci.yml, JavaScript/CSS/Ruby code or the layout files.

For help with failing pipelines reach out in #mr-buddies in Slack