Resolve "Blog Post for Safe Deployments" - now 7/24

Why is this change being made?

Proposal

Following our documentation work in gitlab-org/gitlab#215469 (comment 350734279), we have a few new features around safe deployments that tell a really compelling story when combined together. A blog post would be a great way to inform users about these great capabilities

• Limit the pipeline job concurrency resource_group
• Disallows deployments for old versions
• Deploy Freeze

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

Closes #7857 (closed)