Adds a deprecation notice into 'scheduled-daily-deployments'

Why is this change being made?

We've received feedback that the page shows up in handbook searches and people are referencing it as a current state, while the intention of designs and blueprints is to create a roadmap, so we have added a deprecation notice into scheduled-daily-deployments/index.html.md to indicate so.

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 change relates to any part of the project other than updates to content and/or data files (e.g. team.yml) please make sure to ping @gl-static-site-editor in a comment for a review and merge.
  • If the DRI for the page/s being updated isn't immediate 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

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