[llvm] [workflows] Mention the correct user who makes a /cherry-pick comment (PR #82680)

[Luke Lau via llvm-commits]

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@@ -65,5 +65,5 @@ jobs:
           release-workflow \
           --branch-repo-token ${{ secrets.RELEASE_WORKFLOW_PUSH_SECRET }} \
           --issue-number ${{ github.event.issue.number }} \
-          --requested-by ${{ github.event.issue.user.login }} \
+          --requested-by ${{ (github.event.action == 'opened' && github.event.issue.body.user.login) || github.event.comment.user.login }} \
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lukel97 wrote:

Just skimming through the issue webhook event, is this `body` meant to be bere? It looks to be a string in https://docs.github.com/en/webhooks/webhook-events-and-payloads#issues

https://github.com/llvm/llvm-project/pull/82680