Update branch protection rule instructions

[ashis-baral]

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?

https://docs.github.com/en/repositories/configuring-branches-and-merges-in-your-repository/managing-protected-branches/managing-a-branch-protection-rule#creating-a-branch-protection-rule

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

The article says:

Next to "Branch protection rules", click Add rule.”

This does not match the current UI.

For the current UI:

Under “Branch protection rules”, click “Add classic branch protection rule.”

Additional information

The screenshot shows the current GitHub UI and the location of the button.