[7.17](backport #39540) Allow dependabot report BK status checks

[mergify]

Proposed commit message

This commit adds dependabot to the BK PR Bot allow list to enable status check reporting.

Related issues

https://elastic.slack.com/archives/C0522G6FBNE/p1715667400245839?thread_ts=1715631887.065609&cid=C0522G6FBNE

---

This is an automatic backport of pull request #39540 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of a992601 has failed:

On branch mergify/bp/7.17/pr-39540
Your branch is up to date with 'origin/7.17'.

You are currently cherry-picking commit a992601dac.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .buildkite/pull-requests.json

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[botelastic]

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