Remove the 504 Gateway Timeout for vendor unreachable

https://github.com/badges/shields/issues/529#issuecomment-158550989

Part of #445

Reverts beebab6232

server.js

@@ -213,7 +213,6 @@ function cache(f) {
       }
       var badgeData = getBadgeData('vendor', data);
       badgeData.text[1] = 'unresponsive';
-      ask.res.statusCode = 504;  // Gateway Timeout
       var extension;
       try {
         extension = match[0].split('.').pop();