feat(tests): Replaced toBeFalsy with toBe(false) in approval_check_popover_spec.js

What does this MR do and why?

• This MR replaces toBeFalsy with toBe(false)
• This MR fixes #369636 (closed)

Screenshots or screen recordings

How to set up and validate locally

1. yarn
2. yarn jest ee/spec/frontend/approvals/components/approval_check_popover_spec.js

MR acceptance checklist

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