Remove redundant deprecations reminder

Why is this change being made?

From the 15.5 release post retro:

The task says:

If there are no deprecation announcements for this milestone, do a search to see if there are any open or merged MRs for the current milestone.

What are you supposed to do if you find anything matching the search? It seems like there would be different actions based on if the MRs were already merged or not.

This task is redundant and can be removed from the release post manager's responsibilities. PMs are aware of the deprecation and removal process as part of their workflow and we should allow them to hold themselves accountable for adding deprecations to Docs.

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.
• 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
• 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.

---