Remove .gitlab-ci.yml

.gitlab-ci.yml

-image: haskell:8.6.3
-
-# Change stacks global directory to be inside the project directory,
-# since we can only cache local dependencies.
-variables:
-  STACK_ROOT: "$CI_PROJECT_DIR/.stack-root"
-
-cache:
-  paths:
-    - .stack-root/
-
-test_branch:
-  script:
-    - stack --no-terminal --system-ghc --no-install-ghc build --test --haddock --no-haddock-deps --bench --no-run-benchmarks
-  except:
-    - master
-
-test:
-  script:
-    - stack --no-terminal --system-ghc --no-install-ghc build --copy-bins --test --haddock --no-haddock-deps --bench --no-run-benchmarks
-    - cp -r ~/.local/bin/ copar-linux-binaries
-  only:
-    - master
-  artifacts:
-    name: "${CI_PROJECT_NAME}-linux-binaries"
-    expire_in: 10 yrs
-    paths:
-        - copar-linux-binaries/