Docs: Fix missing braces into code snippet

[HelloAlberuni]

The parameters of useBlockProps should be an object otherwise it generates error.

What?

It adds the missing braces to code snippets using the useBlockProps hook.

Why?

The parameters of the useBlockProps hook must be an object; otherwise, it will throw an error in the console. I've seen another code snippet [in this doc](https://developer.wordpress.org/block-editor/reference-guides/block-api/block-edit-save/#block-wrapper-props passed) passed an object which is the right way.

[github-actions]

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Co-authored-by: HelloAlberuni <alberuni-azad@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[github-actions]

👋 Thanks for your first Pull Request and for helping build the future of Gutenberg and WordPress, @HelloAlberuni! In case you missed it, we'd love to have you join us in our Slack community.

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[Mamaduka]

Thanks for fixing the docs, @HelloAlberuni!

This particular example is auto-generated, and you'll need to fix it in this file https://github.com/WordPress/gutenberg/blob/trunk/packages/block-editor/src/components/block-list/use-block-props/index.js#L52-L58.

Before committing the changes, make sure to run - the npm run docs:build command.