Update the "Build your first block" tutorial based on user feedback

[ndiego]

This is a minor update to the Build your first block tutorial to address feedback noted here. Thanks @silverhoopedge!

create a folder” – I am not sure I understand the purpose - I did not do this step and the tutorial worked okay.
"Therefore, create a new directory (folder) on your computer called “Block Tutorial”

“line 9” — this is relative, after a few file edits, the code referenced was not on line 9 for me
"So open up the file and add the following section after the example in line 9."

[github-actions]

Flaky tests detected in 7ca252b.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/7341808184
📝 Reported issues:

• [Flaky Test] should outdent with children #41428 in /test/e2e/specs/editor/blocks/list.spec.js