Follow up #58306

What?

This PR updates the definition of the shadow property in the block.json schema.

Why?

Current schema allows boolean or object. I think the reason object is allowed is because it assumes the __experimentalSkipSerialization property. However, this property is not exposed on block.json schema. Furthermore, it is not possible to read from the schema whether the default value of shadow is true or false.

How?

I changed the type back to boolean only and defined the default value as false.

I initially simply changed the type to a boolean value as below, but this seems to cause unit tests to fail.

"shadow": {
	"type": "boolean",
	"description": "Allow blocks to define a box shadow.",
	"default": false
},

This is because the actual block.json also defines an object with the __experimentalSkipSerialization property, even though the schema expects only boolean type.

Therefore, in this PR, I limited ourselves to adding the default value (false) and description. Ideally, we might need to update the unit test logic to exclude properties with the __experimental prefix before validating the schema.

Testing Instructions

Verify that the code editor displays the correct definition using the file below.

{
	"$schema": "https://raw.githubusercontent.com/WordPress/gutenberg/block-schema/shadow-boolean/schemas/json/block.json",
	"apiVersion": 2,
	"name": "test/test",
	"title": "Test",
	"supports": {
	}
}

Screenshots or screencast