fix(CI): Fix unknown command error

The 'tabs' command is not available by default on Alpine images, this makes the current pipeline fail. Removing the instruction to fix the issue.

.gitlab-ci.yml

@@ -25,7 +25,6 @@ build-image:
     - echo "DOWNLOAD_URL=http://random.com" >> RELEASE
     - sed -i '14 i \      libatomic1 cron \\' Dockerfile
     - sed -i '45 i \ \n\# Setup crontab for scheduled backups\nRUN { cat; echo \"0 5 * * 6 gitlab-backup create SKIP=registry,builds,artifacts\"; } | crontab -\n\n' Dockerfile
-    - tabs 4
     - sed -i '/gitlab-ctl reconfigure/a \\nif command -v cron\; then\n\techo \"Starting cron daemon...\"\n\tcron\nfi' assets/wrapper
     - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
     - docker build -t $CI_REGISTRY/athens-school/gitlab:$GITLAB_SHORT_VER .