[fix] Dont force `Connection: close` now that Keep-Alive is supported

lib/node-http-proxy.js

@@ -413,10 +413,6 @@ HttpProxy.prototype.proxyRequest = function (req, res, options) {
     headers: req.headers
   };
   
-  // Force the `connection` header to be 'close' until
-  // node.js core re-implements 'keep-alive'.
-  outgoing.headers['connection'] = 'close';
-  
   protocol = _getProtocol(options.https || this.target.https, outgoing);
   
   // Open new HTTP request to internal resource with will act as a reverse proxy pass