🔥(backend) remove outdated GitHub workflow

Clean up CI/CD by deleting obsolete workflow file that is no longer
needed or maintained since we deploy project through private repo.

.github/workflows/deploy.yml

@@ -1,35 +0,0 @@
-name: Deploy
-
-on:
-  push:
-    tags:
-      - 'preprod'
-      - 'production'
-
-
-jobs:
-  notify-argocd:
-    runs-on: ubuntu-latest
-    steps:
-      -
-        name: Checkout repository
-        uses: actions/checkout@v4
-      -
-        name: Call argocd github webhook
-        run: |
-          data='{"ref": "'$GITHUB_REF'","repository": {"html_url":"'$GITHUB_SERVER_URL'/'$GITHUB_REPOSITORY'"}}'
-          sig=$(echo -n ${data} | openssl dgst -sha1 -hmac ''${{ secrets.ARGOCD_WEBHOOK_SECRET }}'' | awk '{print "X-Hub-Signature: sha1="$2}')
-          curl -X POST -H 'X-GitHub-Event:push' -H "Content-Type: application/json" -H "${sig}" --data "${data}" ${{ vars.ARGOCD_WEBHOOK_URL }}
-          sig=$(echo -n ${data} | openssl dgst -sha1 -hmac ''${{ secrets.ARGOCD_PRODUCTION_WEBHOOK_SECRET }}'' | awk '{print "X-Hub-Signature: sha1="$2}')
-          curl -X POST -H 'X-GitHub-Event:push' -H "Content-Type: application/json" -H "${sig}" --data "${data}" ${{ secrets.ARGOCD_PRODUCTION_WEBHOOK_URL }}
-
-  start-test-on-preprod:
-    needs:
-      - notify-argocd
-    runs-on: ubuntu-latest
-    if: startsWith(github.event.ref, 'refs/tags/preprod')
-    steps:
-      -
-        name: Debug
-        run: |
-          echo "Start test when preprod is ready"