http2: fix debugStream method

So it actually logs something when debug is activated.

PR-URL: https://github.com/nodejs/node/pull/45129
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>

lib/internal/http2/core.js

@@ -189,9 +189,10 @@ const { _connectionListener: httpConnectionListener } = http;
 let debug = require('internal/util/debuglog').debuglog('http2', (fn) => {
   debug = fn;
 });
+const debugEnabled = debug.enabled;
 
 function debugStream(id, sessionType, message, ...args) {
-  if (!debug.enabled) {
+  if (!debugEnabled) {
     return;
   }
   debug('Http2Stream %s [Http2Session %s]: ' + message,