Pipeline execution policy editor YAML parsing adds extra characters

Editing a CI code block in the policy editor seems to add an extra | or 2 character to the policy YAML.

Screenshots and recordings

• Screen recording: https://www.awesomescreenshot.com/video/24329829?key=580b1165e81febff6da5339203ecd2a7

Policy editor adds extra character

Steps to reproduce

1. Create a group

2. Go to Settings -> General

3. Toggle the Permissions and group features section

4. Enable Run customized CI YAML file as security policy actions

5. Go to Secure -> Policies

6. Select New policy

7. Select Scan execution policy

8. Select Add new action

9. Select Run CI/CD code

10. Past the following code:

        test job:
            stage: test

11. Observe that the YAML section on the right side contains:

    ci_configuration: |
      |-
        test job:
            stage: test

The correct YAML would be:

ci_configuration: |-
    test job:
        stage: test