Remove leftover Gitlab CI files (#24472)

webapp/channels/build/contrib/gitlab/.gitlab-ci.yml

@@ -1,16 +0,0 @@
-lint:
-  allow_failure: true
-  image: node:buster
-  before_script:
-    - npm ci --ignore-scripts
-    - (cd e2e/playwright && npm ci --ignore-scripts)
-  script:
-    - npm run check-types
-    - npm run check
-
-test:
-  image: node:buster
-  before_script:
-    - npm ci --ignore-scripts
-  script:
-    - npm run test

webapp/channels/build/contrib/gitlab/README.md

@@ -1,7 +0,0 @@
-# GitLab CI/CD configuration for Mattermost
-
-The [.gitlab-ci.yml](./.gitlab-ci.yml) file in this directory provides a [GitLab CI/CD configuration file](https://docs.gitlab.com/ee/ci/yaml/gitlab_ci_yaml.html) that can be used to run linting and unit testing for the Mattermost application.
-
-## Usage
-
-To configure your GitLab instance to use this configuration file (and without having to move it to the base directory in this git repository), you can configure the [`CI_CONFIG_PATH` predefined variable](https://docs.gitlab.com/ee/ci/variables/predefined_variables.html) for the repository in GitLab with the configuration file path (`build/contrib/gitlab/.gitlab-ci.yml`).