Page List Item: Disable block toolbar

[scruffian]

What?

This removes the "more" menu for page list item blocks:
Fixes #46751

Why?

These actions don't make sense on this block as you can't manipulate it directly.

How?

Adds the __experimentalToolbar support to the block.json

Testing Instructions

1. Add a navigation block to a post
2. Add a page list block to the navigation block
3. Open the list view so that you can see the contents of the page list block
4. Check that you can't see/access the "more" menu (under the three dots)
5. Open the block inspector for the navigation block
6. Expand the off canvas editor so that you can see the items inside the page list block
7. Check that the page list items don't have a "more" menu (three dots)

Testing Instructions for Keyboard

As above

Screenshots or screencast

[github-actions]

Flaky tests detected in b38163b.
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/3856721909
📝 Reported issues:

• [Flaky Test] passes the search value in the main inserter when clicking Browse all #45332 in specs/editor/various/inserting-blocks.test.js
• [Flaky Test] should select and deselect with shift and arrow keys #44382 in specs/editor/various/multi-block-selection.test.js
• [Flaky Test] should write over selection #39938 in specs/editor/various/multi-block-selection.test.js

[carolinan]

Neat, I did not know that support already existed. I have tested the PR and it works well.

[scruffian]

Neat, I did not know that support already existed.

Me neither!