gitlab-ci: Remove job building EDK2 firmware binaries

gitlab-ci: Remove job building EDK2 firmware binaries

When we introduced this Gitlab-CI job in commit 71920809ce
("gitlab-ci.yml: Add jobs to build EDK2 firmware binaries"),
the naive plan was to have reproducible binaries by downloading
what this job would build, testing it and eventually committing
it. With retrospective, nothing happened 3 years later and this
job is just bitrotting:

  Step 1/3 : FROM ubuntu:18.04
  18.04: Pulling from library/ubuntu
  mediaType in manifest should be
  'application/vnd.docker.distribution.manifest.v2+json' not
  'application/vnd.oci.image.manifest.v1+json'

Remove this job to avoid wasting maintenance and CI ressources.

Reported-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20230310133247.39268-1-philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>