Resolve "Resolve eslint errors in node scripts"

What does this MR do and why?

• Config is adjusted to lint .cjs files, in addition to .js and .vue files
• Eslint warnings in the .cjs files are resolved

Screenshots, screen recordings, or links to review app

N/A

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/technical-writing-group/gitlab-docs-hugo/-/blob/main/doc/setup.md.
2. Run make lint-frontend, it should be a clean output.
3. Check the scripts that were changed for any logic issues.

• __tests__/navigation/check_menu_links.cjs
• scripts/migration/check_history_newlines.cjs
• scripts/check_codeblocks.cjs
• scripts/check_elastic_key_permissions.cjs
• scripts/pages_not_in_nav.cjs

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 #154 (closed)