Accordion panel item: Disable edit as HTML support

[shimotmk]

What?

This PR disables HTML editing support for Accordion panel and item blocks.
A similar PRs: #69374, #11785, #39318, #49426 #55656.

Why?

Editing these wrapper blocks in HTML directly is fragile and prone to breaking the users' content. HTML editing should be left to leaf-blocks.

#11785 (comment)

Testing Instructions

1. Open a Post or Page.
2. Insert a Accordion block.
3. Verify that the Edit as HTML action is not available for Accordion Items and Accordion Panels.

Screenshots or screencast

Before	After

[github-actions]

Flaky tests detected in df5809f.
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/18307657005
📝 Reported issues:

• [Flaky Test] Can add submenu item using the keyboard #71966 in /test/e2e/specs/editor/blocks/navigation.spec.js
• [Flaky Test] Can add submenu item(custom-link) using the keyboard #72064 in /test/e2e/specs/editor/blocks/navigation.spec.js
• [Flaky Test] Deleting items #72065 in /test/e2e/specs/editor/blocks/navigation.spec.js
• [Flaky Test] Focus management when creating navigation links #71108 in /test/e2e/specs/editor/blocks/navigation.spec.js
• [Flaky Test] ensures List View global shortcut works properly #51533 in /test/e2e/specs/editor/various/list-view.spec.js

[github-actions]

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Co-authored-by: shimotmk <shimotomoki@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[Mamaduka]

Makes sense. Thanks, @shimotmk!

[shimotmk]

@Mamaduka
Thanks for the review. Can I merge it?

[Mamaduka]

@shimotmk, of course.

[Mamaduka]

@shimotmk, it's not a big deal, but I would recommend editing the commit title before merging to match the PR title.

[shimotmk]

@Mamaduka
Thank you!
So everyone does that.
https://github.com/WordPress/gutenberg/commits/trunk/
I'll be more careful next time.