Add a UI description for OBS_REBUILD_DISABLED
GitLab can show a textual description for variables that can be set when manually triggering a pipeline, see https://docs.gitlab.com/ee/ci/yaml/index.html#variablesdescription
GitLab can show a textual description for variables that can be set when manually triggering a pipeline, see https://docs.gitlab.com/ee/ci/yaml/index.html#variablesdescription