[8.14](backport #40026) [CI] Remove elastic-agent trigger from pull-requests.json

[mergify[bot]]

Proposed commit message

Removes elastic-agent entry from pull-requests.json. This PR makes it being triggered by the root pipeline instead.

Checklist

• [ ] My code follows the style guidelines of this project
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] I have made corresponding change to the default configuration files
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Disruptive User Impact

Author's Checklist

• [ ]

How to test this PR locally

Related issues

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Use cases

Screenshots

Logs

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This is an automatic backport of pull request #40026 done by Mergify.

[mergify[bot]]

Cherry-pick of c2b2983c1825dcf7dabf64c4a04ce9cf34814fce has failed:

On branch mergify/bp/8.14/pr-40026
Your branch is up to date with 'origin/8.14'.

You are currently cherry-picking commit c2b2983c18.
  (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[bot]]

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