Make Kong respect target server header

kong.yml

@@ -117,7 +117,8 @@ nginx: |
         proxy_set_header X-Real-IP $remote_addr;
         proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_pass $backend_url;
-
+        proxy_pass_header Server;
+        
         # Add additional response headers
         header_filter_by_lua 'kong.exec_plugins_header_filter()';