chore: Use test container for testing fmriprep-docker (nipreps#3520)

Not sure how we missed this in nipreps#3503, but we need to use a downloaded
image to avoid reading stdin in fmriprep-docker.

Author: effigies

.circleci/config.yml

@@ -391,6 +391,7 @@ jobs:
       - docker/install-docker-credential-helper
       - run: *docker_auth
       - run: *setup_docker_registry
+      - run: *pull_from_registry
       - run: *pull_test_image_from_registry
       - run:
           name: Run fMRIPrep tests