Editor: disable `shadow.defaultPresets` in default `theme.json`.

This is a follow-up to [57717] to ensure that classic themes without a `theme.json` file or without `appearanceTools: true` in `theme.json` do not have shadow controls by default.

Props wildworks, vcanales, madhudollu, swissspidy, youknowriad.
Fixes #60633
Built from https://develop.svn.wordpress.org/trunk@57827


git-svn-id: http://core.svn.wordpress.org/trunk@57328 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/theme.json

@@ -191,7 +191,7 @@
 			"text": true
 		},
 		"shadow": {
-			"defaultPresets": true,
+			"defaultPresets": false,
 			"presets": [
 				{
 					"name": "Natural",

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.6-alpha-57826';
+$wp_version = '6.6-alpha-57827';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.