FIX (attempt) jupyter book preview in PRs (#745)

.github/workflows/jupyter-book-pr-preview.yml

@@ -19,20 +19,18 @@ jobs:
           sha: ${{ github.event.workflow_run.head_sha }}
           context: 'JupyterBook preview'
 
+      - name: Download artifacts
+        run: gh run download --name jupyter-book ${{ github.event.workflow_run.id }}
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Get pull request number
         id: pull-request-number
         run: |
-          export PULL_REQUEST_NUMBER=${{github.event.workflow_run.pull_requests[0].number}}
+          export PULL_REQUEST_NUMBER=`cat pull_request_number`
           echo "PULL_REQUEST_NUMBER=$PULL_REQUEST_NUMBER"
           echo "result=${PULL_REQUEST_NUMBER}" >> $GITHUB_OUTPUT
 
-      - uses: dawidd6/action-download-artifact@v2
-        with:
-          github_token: ${{secrets.GITHUB_TOKEN}}
-          workflow: deploy-gh-pages.yml
-          pr: ${{steps.pull-request-number.outputs.result}}
-          name: jupyter-book
-
       - uses: actions/setup-node@v3
         with:
           node-version: '16'