ci: remove broken node-delete-preview.yml workflow

Old previews should be deleted by the cronjob
running on the `download.delta.chat` server.

.github/workflows/node-delete-preview.yml

@@ -1,31 +0,0 @@
-# documentation: https://github.com/deltachat/sysadmin/tree/master/download.delta.chat
-name: Delete node PR previews
-
-on:
-  pull_request:
-    types: [closed]
-
-jobs:
-  delete:
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Get Pull Request ID
-        id: getid
-        run: |
-          export PULLREQUEST_ID=$(jq .number < $GITHUB_EVENT_PATH)
-          echo "prid=$PULLREQUEST_ID" >> $GITHUB_OUTPUT
-      - name: Renaming
-        run: |
-          # create empty file to copy it over the outdated deliverable on download.delta.chat
-          echo "This preview build is outdated and has been removed." > empty
-          cp empty deltachat-node-${{ steps.getid.outputs.prid }}.tar.gz
-      - name: Replace builds with dummy files
-        uses: horochx/deploy-via-scp@v1.0.1
-        with:
-          user: ${{ secrets.USERNAME }}
-          key: ${{ secrets.SSH_KEY }}
-          host: "download.delta.chat"
-          port: 22
-          local: "deltachat-node-${{ steps.getid.outputs.prid }}.tar.gz"
-          remote: "/var/www/html/download/node/preview/"