DataForm: remove FormFieldVisibility

[oandregal]

What?

This removes a piece of code that is not used, we forgot removing it in a past refactoring.

Testing Instructions

Build the project, load the Pages page, open the QuickEdit experiment and verify nothing breaks.

[github-actions]

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Co-authored-by: oandregal <oandregal@git.wordpress.org>
Co-authored-by: louwie17 <louwie17@git.wordpress.org>

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[github-actions]

Flaky tests detected in 7d34916.
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/12434546039
📝 Reported issues:

• [Flaky Test] Navigates the items list via UP/DOWN arrow keys #64334 in /test/e2e/specs/site-editor/dataviews-list-layout-keyboard.spec.js
• [Flaky Test] submenu click on the arrow interactions #61884 in /test/e2e/specs/editor/blocks/navigation-frontend-interactivity.spec.js

[louwie17]

Thanks @oandregal for cleaning this up, I guess I missed this with that last layout PR, thanks for removing this :)
Everything still tested well 💯 👍