fix(challenges): fix flex direction row regex

[joshalling]

ISSUES CLOSED: #260

Description

I improved regex for this challenge a little bit by ensuring the flex-direction declarations are in the right rules while also removing the line number restriction.

I also thought about using jQuery in the tests, but that is not possible here because row is already the default value of flex-direction, so you could pass the challenge without doing anything.

Pre-Submission Checklist

• [x] Your pull request targets the dev branch.
• [x] Branch starts with either fix/, feature/, or translate/ (e.g. fix/challenge-tests)
• [x] All new and existing tests pass the command npm test.
• [x] Use npm run commit to generate a conventional commit message. Learn more here: https://conventionalcommits.org/#why-use-conventional-commits
• [x] The changes were done locally on your machine and NOT GitHub web interface. If they were done on the web interface you have ensured that you are creating conventional commit messages.

Checklist:

• [x] Tested changes locally.
• [x] Addressed currently open issue (replace XXXXX with an issue no in next line)

Closes #260

[scissorsneedfoodtoo]

@joshalling, thank you for documenting this issue and submitting this fix! Checked it out and everything LGTM :+1: