Add Label UI is unusable in Test Case sidebar

Description

Noticed on .com https://gitlab.com/gitlab-org/gitlab-web-ide/-/quality/test_cases/33

• When creating a label from the test case side bar, the user is unable to complete the action as the top is behind the header.

Kapture_2022-10-31_at_20.21.40

Steps to reproduce

1. Set the viewport (window) height to less than 570px. For example 500px.
2. Go to a test case. For example, https://gitlab.com/gitlab-org/gitlab-web-ide/-/quality/test_cases/33
3. Edit the label
4. Create group label

Expected behaviour

Dropdown is below the trigger, and not obscured by other UI elements.

Before	After