Navigation: Add missing empty space to print out valid HTML.

[juanfra]

What?

Adding an empty space to have the navigation block producing valid HTML.

Fixes #59238

Why?

Because if not, there are two attributes together.

How?

Adding an empty space.

Testing Instructions

1. Open a site with TT4.
2. Set up a navigation menu.
3. Visit the front end, view the page source, and confirm that there's an empty space between data-wp-interactive="core/navigation" and the following data attribute of the nav element.

[github-actions]

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The following contributors have not linked their GitHub and WordPress.org accounts: @gyurmey2.

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Co-authored-by: juanfra <juanfra@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: huzaifaalmesbah <huzaifaalmesbah@git.wordpress.org>

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[huzaifaalmesbah]

I tested your PR, and it successfully addressed the issue. nice work

[github-actions]

Flaky tests detected in c95a2ee.
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/8002508355
📝 Reported issues:

• [Flaky Test] default to the only existing classic menu if there are no block menus #48033 in /test/e2e/specs/editor/blocks/navigation.spec.js

[Mamaduka]

Thank you, @juanfra!

[getdave]

I just cherry-picked this PR to the cherry-pick-wp-6-5-beta-3 branch to get it included in the next release: 266b4d2