Since c8e67939 ("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>