Use v-show to catch errors

What does this MR do and why?

Use v-show to catch errors

• allows for testing of visibility

Changelog: changed

EE: true

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After
	No change

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license
2. Navigate to a project => Secure => Policies => New policy => Merge request approval policy => yaml mode
3. Remove the fallback_behavior section
4. Save the policy and merge it
5. Navigate to the project => Secure => Policies => Select the policy
6. Verify the drawer appears properly without the fallback section

Related to #464368 (closed)