Update .gitlab-ci.yml

Removed debug ls

.gitlab-ci.yml

-image: pandoc/latex:latest
+image:
+  name: pandoc/latex
+  entrypoint: [""]
 
 Documentation:
+  tags:
+    - docker
+  only:
+    changes:
+      - documentation/design/*.md
   script:
     - cd documentation/design
     - pandoc --filter pandoc-citeproc --bibliography=bibliography.bib --csl=acm-sig-proceedings.csl --variable papersize=a4paper -s *.md -o documentation.pdf
-    - ls
   artifacts:
     paths:
       - documentation/design/documentation.pdf
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