[BE] Delete push_nightly_docker_ghcr (#88748)
As it seems to be duplicating the functionality of `docker-release.yml` and have not produced a valid build in last 16 days, according to https://github.com/pytorch/pytorch/actions/workflows/push_nightly_docker_ghcr.yml
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88748
Approved by: https://github.com/seemethere
