gitlab ci: revert

.gitlab-ci.yml

@@ -1,23 +0,0 @@
-workflow:
-  rules:
-    - if: $CI_PIPELINE_SOURCE == 'merge_request_event'
-    - if: $CI_COMMIT_TAG
-    - if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH
-
-stages:
-  - check
-  - update
-
-default:
-  image: "nixos/nix:latest"
-
-check-jobs:
-  stage: check
-  script:
-    - nix --extra-experimental-features 'flakes nix-command' flake check
-
-update-jobs:
-  stage: update
-  script:
-    - nix --extra-experimental-features 'flakes nix-command' flake update
-