Fix rotation angle on menu icons

What does this MR do and why?

Chevron icons on the menu are over-rotated by 5 degrees when toggled closed.

Screenshots, screen recordings, or links to review app

Before	After

Review app: https://1778-tilty-chevs.docs.gitlab-review.app/ee/administration/configure.html

How to set up and validate locally

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

1. Configure a local GitLab Docs environment: https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/doc/setup.md.
2. View a page with the global nav. Chevrons should rotate 45 degrees either way when toggled.

Merge request acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this merge request.

Closes #1778 (closed)