Fix GitLab beginners' guide (#231)

Author: 0x2b3bfa0

content/docs/start/gitlab.md

@@ -61,15 +61,11 @@ Here, we'll walk through a tutorial to start using CML on GitLab.
    into a new file `.gitlab-ci.yml` and save.
 
    ```yaml
-   train-model:
+   train-and-report:
      image: iterativeai/cml:0-dvc2-base1
      script:
        - pip install -r requirements.txt
        - python train.py
-   create-cml-report:
-     needs: train-model
-     image: iterativeai/cml:0-dvc2-base1
-     script:
        - cat metrics.txt >> report.md
        - cml publish plot.png --md >> report.md
        - cml send-comment report.md