fix: add branch deletion permissions to 'autoclose superseded PRs' workflow

[nlucero]

Description

• The workflow to autoclose superseded automated PRs was lacking contents: write permissions, necessary to delete branches
• Additionally, make it log a message if there are no PRs to close

References

Testing

Checklist

• I've read and followed CONTRIBUTING.md.
• I've tested the site build for this change locally.
• I've made appropriate docs updates for any code or config changes.
• I've coordinated with the Product Docs and/or Docs Management team about non-trivial changes.

[mintlify]

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Project	Status	Preview	Updated (UTC)
auth0	🔴 Failed	–	May 22, 2026, 7:48 PM

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