Fix the sample compilation in the API server container build

Signed-off-by: mprahl <[email protected]>

backend/Dockerfile

@@ -54,7 +54,7 @@ COPY backend/src/apiserver/config/sample_config.json /samples/
 # Compiling the preloaded samples.
 # The default image is replaced with the GCR-hosted python image.
 RUN set -e; \
-    < /samples/sample_config.json jq .[].file --raw-output | while read pipeline_yaml; do \
+    < /samples/sample_config.json jq ".pipelines[].file" --raw-output | while read pipeline_yaml; do \
     pipeline_py="${pipeline_yaml%.yaml}"; \
     python3 "$pipeline_py"; \
     done