Complete test script for incident management CMS
#### What's this issue all about? (Background and context) This issue is for completing the first part of Step 4 of the [CMS process](https://about.gitlab.com/handbook/engineering/ux/category-maturity-scorecards/#step-4-complete-the-test-script-and-conduct-the-research) for incident management: Complete test script. Research won't be conducted until internal teams are dogfooding in Q1 of next year so that work has been broken out into a [separate issue](https://gitlab.com/gitlab-org/ux-research/-/issues/1221). [Script google doc](https://docs.google.com/document/d/1zWgTZzqRWWIhYQw9twyn_wYW9omJ0gokfZqwxaINUrI/edit?usp=sharing)
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