chore: remove unused .gitlab-ci.yml

No longer needed after migration to Gitea Actions.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitlab-ci.yml

@@ -1,22 +0,0 @@
-include:
-- template: 'Workflows/MergeRequest-Pipelines.gitlab-ci.yml'
-- project: unboundsoftware/ci-templates
-  file: Defaults.gitlab-ci.yml
-- project: unboundsoftware/ci-templates
-  file: Release.gitlab-ci.yml
-- project: unboundsoftware/ci-templates
-  file: Pre-Commit-Go.gitlab-ci.yml
-
-stages:
-- build
-
-image: buildtool/build-tools:${BUILDTOOLS_VERSION}
-
-build:
-  stage: build
-  script:
-  - build
-  - curl -Os https://uploader.codecov.io/latest/linux/codecov
-  - chmod +x codecov
-  - ./codecov -t ${CODECOV_TOKEN} -R $CI_PROJECT_DIR -C $CI_COMMIT_SHA -r $CI_PROJECT_PATH
-  - push