Run untagged jobs.

Set the runners to run untagged jobs (I only enabled tagging to run
specific jobs in specific runners, the untagged jobs should still run
wherever).

docker-compose.yml

@@ -9,6 +9,7 @@ services:
       DOCKER_IMAGE: docker:19.03
       REGISTRATION_TOKEN: "${REGISTRATION_TOKEN}"
       RUNNER_NAME: "${RUNNER_NAME}"
+      REGISTER_RUN_UNTAGGED: "${RUN_UNTAGGED:-true}"
       RUNNER_TAG_LIST: "${RUNNER_NAME}"
     image: adarnimrod/gitlab-runner
     restart: always