Rosetta customizations: Fix the return object when settings are custo…

…mized.

This should return `WP_Theme_JSON_Data` (as the phpdoc claims), but was accidentally using `WP_Theme_JSON` instead. Previously this worked, but after r58185-core the use of this class triggered a fatal error. Switching to the correct class fixes the error.

source/wp-content/themes/wporg-parent-2021/inc/rosetta-styles.php

@@ -27,7 +27,7 @@ function inject_i18n_customizations( $theme_json ) {
 		'settings' => $locale_settings,
 	);
 
-	return new \WP_Theme_JSON( $config, 'custom' );
+	return new \WP_Theme_JSON_Data( $config, 'custom' );
 }
 
 /**