Fix: contributor/author synced pattern visibility

[karthikeya-io]

What?

Closes #70222

Fixes the "Block has been deleted or is unavailable." message shown for synced patterns when viewed by users without edit permissions for the synced pattern (e.g., Contributors or Authors).

Why?

Currently, useEntityRecord and useEntityBlockEditor are used to retrieve the synced pattern in the ReusableBlockEdit component. These hooks call the endpoint /index.php?rest_route=/wp/v2/blocks/id&context=edit&_locale=user which returns a 403 error for contributors and authors who lack edit access to the pattern. That leads to the “Block has been deleted or is unavailable.” message until another endpoint updates the store with the blocks.

How?

To prevent this, if the user lacks edit capabilities we fall back to using useEntityRecords to fetch the synced pattern, which does not produce a 403 error.

Testing Instructions

1. Log in as an admin, create a synced pattern, and add it to a post.
2. Log in as a contributor or author, and open the post containing the synced pattern.
3. Confirm that the message “Block has been deleted or is unavailable.” is not displayed for the pattern.

Testing Instructions for Keyboard

Same

Screenshots or screencast

Before	After

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Co-authored-by: karthikeya-io <karthikeya01@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>

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