Lower wp-supercache max-age to 5 mins

docker/wp-config.php

@@ -117,7 +117,7 @@ define('COOKIEHASH', '7d12c307721c1cbe9412c639209d72aa');
 
 /* Custom Cache-Control headers for WP-SuperCache.
  * These are set to match our edge nginx caches.
-define('WPSC_CACHE_CONTROL_HEADER', 'max-age=600');
+define('WPSC_CACHE_CONTROL_HEADER', 'max-age=300');
 
 /**#@+
  * Authentication Unique Keys and Salts.