Added tests against nested divs custom headding challenge

[dhcodes]

Pre-Submission Checklist

• Your pull request targets the staging branch of FreeCodeCamp.
• Branch starts with either fix/, feature/, or translate/ (e.g. fix/signin-issue)
• You have only one commit (if not, squash them into one commit).
• All new and existing tests pass the command npm run test-challenges. Use git commit --amend to amend any fixes.

Type of Change

• Small bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds new functionality)
• Breaking change (fix or feature that would change existing functionality)
• Add new translation (feature adding new translations)

Checklist:

• Tested changes locally.
• Closes currently open issue (replace XXXX with an issue no): Closes Bug with task "Create a Custom Heading" #9967

Description

I added to the existing tests two statements that check whether each

has a nested div within it. It corrects #9967 as it doesn't allow the user to nest a div within a div and still pass the challenge and the message still fits well enough imho.

[raisedadead]

✨ ✨ LGTM. ✨ ✨

Thanks Dylan.