chore: remove gitlab artifacts to avoid slow uploads

Remove artifacts uploading from the build stage. Since we use a shared
docker socket on the same runner host, the package stage can access the
locally built jar file directly without needing gitlab coordinator upload/download.

.gitlab-ci.yml

@@ -19,10 +19,6 @@ build:
     - chmod +x gradlew
   script:
     - ./gradlew bootJar -x test -PartefactVersion="$CI_COMMIT_TAG"
-  artifacts:
-    paths:
-      - build/libs/*.jar
-    expire_in: 30 min
   rules:
     - if: $CI_COMMIT_TAG