VIP-Go: Add ruleset test for cron min interval

Author: GaryJones

WordPress-VIP-Go/ruleset-test.inc

@@ -577,3 +577,13 @@ $_SERVER["REMOTE_ADDR"]; // Error.
 
 // WordPress.CodeAnalysis.AssignmentInTernaryCondition
 $var = ($a = 123) ? $a : 0; // Warning.
+
+// WordPress.WP.CronInterval
+function my_add_weekly( $schedules ) {
+	$schedules['every_30_seconds'] = array(
+		'interval' => 30,
+		'display' => __( 'Once every 30 seconds' )
+	);
+	return $schedules;
+}
+add_filter( 'cron_schedules', 'my_add_weekly'); // Warning.

WordPress-VIP-Go/ruleset-test.php

@@ -232,6 +232,7 @@
 		550 => 1,
 		556 => 1,
 		579 => 1,
+		589 => 1,
 	],
 	'messages' => [
 		7   => [