Bump stylesheet cache group after #3866 (#3880)

includes/sanitizers/class-amp-style-sanitizer.php

@@ -1394,7 +1394,7 @@ private function fetch_external_stylesheet( $url ) {
 	private function process_stylesheet( $stylesheet, $options = [] ) {
 		$parsed      = null;
 		$cache_key   = null;
-		$cache_group = 'amp-parsed-stylesheet-v21'; // This should be bumped whenever the PHP-CSS-Parser is updated or parsed format is updated.
+		$cache_group = 'amp-parsed-stylesheet-v22'; // This should be bumped whenever the PHP-CSS-Parser is updated or parsed format is updated.
 
 		$cache_impacting_options = array_merge(
 			wp_array_slice_assoc(