update `gh clone` command for `Cloning a repository`

[brignano]

Code of Conduct

• I have read and agree to the GitHub Docs project's Code of Conduct

What article on docs.github.com is affected?

Cloning a repository

What part(s) of the article would you like to see updated?

gh clone should be gh repo clone

Additional information

I will create a pull request with this change.

[welcome]

Thanks for opening this issue. A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[cmwilson21]

@brignano Thank you for opening an issue and linking it to your PR! ✨