debian/apertis/gitlab-ci.yml: Drop since we use an external definition

Apertis has moved to using external references in the CI config path setting
for the packagign repositories, so the gitlab-ci.yml embedded in the
repository is no longer needed.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>

debian/apertis/gitlab-ci.yml

-include:
-  - project: 'infrastructure/ci-package-builder'
-    file: '/ci-package-builder.yml'