[IM] Update prefix whois as whois.bgpmon.net no longer available - via @listerr #891

Author: barryo

Diff for: config/ixp_api.php

@@ -139,7 +139,7 @@
         ],
 
         'prefix' => [
-            'host' => env( 'IXP_API_WHOIS_PREFIX_HOST', 'whois.bgpmon.net' ),
+            'host' => env( 'IXP_API_WHOIS_PREFIX_HOST', 'whois.radb.net' ),
             'port' => env( 'IXP_API_WHOIS_PREFIX_PORT', 43 ),
         ],
     ],