Nightly tag push is not skipped in scheduled builds (apache#10597)

With recent refactors, nightly tag was not pushed on
scheduled event because it was depending on pushing images
to github registry. Pushing images to github registry is
skipped on scheduled builds, so pushing tag was also skipped.

.github/workflows/ci.yml

@@ -773,8 +773,6 @@ jobs:
       - tests-kubernetes
       - constraints-push
       - prepare-backport-packages
-      - push-prod-images-to-github-registry
-      - push-ci-images-to-github-registry
     if: github.event_name == 'schedule' &&  github.repository == 'apache/airflow'
     steps:
       - name: "Checkout ${{ github.ref }} ( ${{ github.sha }} )"