Revert change to layout selectors

lib/class-wp-theme-json-gutenberg.php

@@ -1744,7 +1744,7 @@ protected function get_layout_styles( $block_metadata, $types = array() ) {
 										$spacing_rule['selector']
 									);
 								} else {
-									$format          = static::ROOT_BLOCK_SELECTOR === $selector ? ':root :where(.%2$s %3$s)' : ':root :where(%1$s-%2$s %3$s)';
+									$format          = static::ROOT_BLOCK_SELECTOR === $selector ? '.%2$s %3$s' : '%1$s-%2$s %3$s';
 									$layout_selector = sprintf(
 										$format,
 										$selector,