lib: change concatenated string to template

PR-URL: #16925
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>

lib/_http_common.js

@@ -78,7 +78,7 @@ function parserOnHeadersComplete(versionMajor, versionMinor, headers, method,
   parser.incoming = new IncomingMessage(parser.socket);
   parser.incoming.httpVersionMajor = versionMajor;
   parser.incoming.httpVersionMinor = versionMinor;
-  parser.incoming.httpVersion = versionMajor + '.' + versionMinor;
+  parser.incoming.httpVersion = `${versionMajor}.${versionMinor}`;
   parser.incoming.url = url;
 
   var n = headers.length;