Update Popperjs dependency to next major version

Replaces deprecated: https://www.npmjs.com/package/popper.js with newer https://www.npmjs.com/package/@popperjs/core.

• Before: https://docs.gitlab.com/ee/user/project/
• After: http://eread-update-popperjs-dependency.178.62.207.141.nip.io/ee/user/project/