Update Release Post automation to build bug, ux, and performance URL

Why is this change being made?

The sample files that are generated with each release post require the release post manager to edit the URL with the updated milestone and applicable labels.

This has led to confusion in previous milestones and most recently in 15.1.

This MR updates the templates and the automation to build the URL for the release post manager to ensure consistency and avoid confusion.

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
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  • 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
• 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.

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