Switch from node-sass to sass

node-sass is deprecated and this is the suggested replacement:
facebook/create-react-app#10779

Author: PhilippWendler

.gitlab-ci.yml

@@ -130,7 +130,6 @@ javascript-build:
   before_script:
     - cd benchexec/tablegenerator/react-table
     - npm install
-    - npm rebuild node-sass
   script:
     - npm run build
     - git diff --stat --exit-code