fix: harden automated release workflow

Author: vastsa

.github/workflows/release-please.yml

@@ -30,8 +30,10 @@ jobs:
         if: ${{ steps.release.outputs.prs_created == 'true' }}
         env:
           GH_TOKEN: ${{ github.token }}
-          RELEASE_PR: ${{ fromJSON(steps.release.outputs.pr).number }}
+          GH_REPO: ${{ github.repository }}
+          RELEASE_PR_JSON: ${{ steps.release.outputs.pr }}
         run: |
+          RELEASE_PR="$(jq -r '.number' <<< "$RELEASE_PR_JSON")"
           for attempt in {1..120}; do
             if gh pr merge "$RELEASE_PR" --squash --delete-branch; then
               break