Editor: Unset reference used in foreach statement.

In PHP it is a good practice to unset $value if it was created by reference in a foreach loop, as the reference is still valid outside the loop, and this avoids accidental bugs.

Props get_dave.
Fixes #60326.

git-svn-id: https://develop.svn.wordpress.org/trunk@57340 602fd350-edb4-49c9-b593-d223f7449a82

Author: youknowriad

src/wp-includes/class-wp-theme-json.php

@@ -1070,6 +1070,7 @@ public function get_stylesheet( $types = array( 'variables', 'styles', 'presets'
 			foreach ( $style_nodes as &$node ) {
 				$node['selector'] = static::scope_selector( $options['scope'], $node['selector'] );
 			}
+			unset( $node );
 		}
 
 		if ( ! empty( $options['root_selector'] ) ) {