nuke all the CI content because we don't use any of these things rn

.gitlab-ci.yml

 image: gitlab.kwant-project.org:5005/qt/research-docker
-
-stages:
-  - run analysis
-  - build documents
-
-variables:
-  GIT_SUBMODULE_STRATEGY: recursive
-
-before_script:
-  - shopt -s nullglob  # sane behaviour when globs do not match
-  - pip install gitlab-ci-tools  # for last-good-build
-  - LAST_GOOD_SHA=$(last-good-build || echo '')
-
-.pdf-build:
-  stage: build documents
-  script:
-    - cd $CWD
-    - if [ -d images ]; then
-    -   cd images
-    -   for image in *.svg; do
-    -     inkscape -o "${image%.*}.pdf" $image
-    -   done
-    -   cd ..
-    -  fi
-    - for tex in *.tex; do
-    -   if grep "documentclass" $tex >/dev/null; then
-    -     latexmk -pdf $tex
-    -     DIFF="$(git diff $LAST_GOOD_SHA -- $tex || echo '')"
-    -     OLD_EXISTS="$(git ls-tree --name-only $LAST_GOOD_SHA | grep -x $tex || echo '')"
-    -     if [ "$LAST_GOOD_SHA" ] && [ "$DIFF" ] && [ "$OLD_EXISTS" ]; then
-    -       git show $LAST_GOOD_SHA:$CWD/$tex > old_$tex
-    -       latexdiff old_$tex $tex > diff_$tex || true
-    -       rm old_$tex
-    -       latexmk -pdf diff_$tex || true
-    -     fi
-    -   fi
-    - done
-
-build notes:
-  extends: .pdf-build
-  variables:
-    CWD: notes
-  artifacts:
-    paths:
-      - notes/*.pdf
-    expire_in: 1 month
-
-build publication:
-  extends: .pdf-build
-  variables:
-    CWD: publication
-  after_script:
-    - mkdir -p public && cp -r $CWD/*.pdf public
-  artifacts:
-    paths:
-      - publication/*.pdf
-    expire_in: 1 month
-  stage: build documents