gitlab: explicitly reference the upstream registry

Since c8e6793903 ("containers.yml: build with docker.py tooling") we
don't need to manually pull stuff from the upstream repository. Just
set the -r field to explicitly use that rather than the current
registry.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Willian Rampazzo <willianr@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20210520174303.12310-3-alex.bennee@linaro.org>

.gitlab-ci.d/containers.yml

@@ -12,10 +12,9 @@
   script:
     - echo "TAG:$TAG"
     - echo "COMMON_TAG:$COMMON_TAG"
-    - docker pull "$TAG" || docker pull "$COMMON_TAG" || true
     - ./tests/docker/docker.py --engine docker build
           -t "qemu/$NAME" -f "tests/docker/dockerfiles/$NAME.docker"
-          -r $CI_REGISTRY_IMAGE
+          -r $CI_REGISTRY/qemu-project/qemu
     - docker tag "qemu/$NAME" "$TAG"
     - docker push "$TAG"
   after_script: