[Documentation] Improve tutorial example code write

[hori031617]

I tried tutorial.

3. Delete all files in the src/ folder of the new project.

I think that good example code here.
For example rm -f src/*
Because, I had a misunderstanding remove src directory.

Thank you.

[bvaughn]

Thank you for filing this issue! 😄

The documentation and source code for reactjs.org now lives in a different repository: reactjs/reactjs.org. (For more info on why we made this move, see issue #11075.)

I've moved your issue to the new repo: reactjs/react.dev#71

Let's continue the discussion there! Sorry for the inconvenience.