Simplify pipeline to avoid passing too big artifacts

.gitlab-ci.yml

-install:
-  stage: .pre
-  image: docker.io/node:current
-  script:
-    - npm ci
-  artifacts:
-    paths:
-      - node_modules
-
-upstream_tests:
-  stage: test
-  image: docker.io/node:current
-  script:
-    - npm run test:ci
-  artifacts:
-    when: always
-    paths:
-      - junit.xml
-    reports:
-      junit: junit.xml
-
 pages:
   stage: deploy
   image: docker.io/node:current
-  script:
+  before_script:
+    - npm ci
     - npm run build
+  script:
     - rm -rf public
     - cp -r demo/dist public
   artifacts: