http2: comment on usage of Object.create(null)

Refs: https://github.com/nodejs/node/issues/29829

PR-URL: https://github.com/nodejs/node/pull/33183
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/internal/http2/compat.js

@@ -287,6 +287,9 @@ class Http2ServerRequest extends Readable {
       closed: false,
       didRead: false,
     };
+    // Headers in HTTP/1 are not initialized using Object.create(null) which,
+    // although preferable, would simply break too much code. Ergo header
+    // initialization using Object.create(null) in HTTP/2 is intentional.
     this[kHeaders] = headers;
     this[kRawHeaders] = rawHeaders;
     this[kTrailers] = {};