http: add note about timer unref

PR-URL: #34143
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/_http_server.js

@@ -588,6 +588,10 @@ function socketOnData(server, socket, parser, state, d) {
 }
 
 function onParserExecute(server, socket, parser, state, ret) {
+  // When underlying `net.Socket` instance is consumed - no
+  // `data` events are emitted, and thus `socket.setTimeout` fires the
+  // callback even if the data is constantly flowing into the socket.
+  // See, https://github.com/nodejs/node/commit/ec2822adaad76b126b5cccdeaa1addf2376c9aa6
   socket._unrefTimer();
   debug('SERVER socketOnParserExecute %d', ret);
   onParserExecuteCommon(server, socket, parser, state, ret, undefined);