ci: revert commit 54f04b41

Use image paritytech/ci-linux:production for 'labels' and 'quality' stages.
We don't need to force a specific Debian release as this image is not used
for the 'build' stage anymore.

.gitlab-ci.yml

@@ -41,7 +41,7 @@ check_labels:
     - ./scripts/check_labels.sh $CI_MERGE_REQUEST_LABELS $CI_MERGE_REQUEST_MILESTONE
 
 .env:
-  image: paritytech/ci-linux:1.68.2-buster
+  image: paritytech/ci-linux:production
   tags:
     - podman