http2: remove no longer userful options.selectPadding

This is a followup cleanup on a previous PR. Current source code and doc
explicitly states that `selectPadding` has been removed for all exports.

Refs: #29144
Refs: https://nodejs.org/api/http2.html
PR-URL: #58373
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rafael Gonzaga <rafael.nunu@hotmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: hkleungai

lib/internal/http2/core.js

@@ -247,7 +247,6 @@ const kPendingRequestCalls = Symbol('kPendingRequestCalls');
 const kProceed = Symbol('proceed');
 const kRemoteSettings = Symbol('remote-settings');
 const kRequestAsyncResource = Symbol('requestAsyncResource');
-const kSelectPadding = Symbol('select-padding');
 const kSentHeaders = Symbol('sent-headers');
 const kSentTrailers = Symbol('sent-trailers');
 const kServer = Symbol('server');
@@ -1100,8 +1099,6 @@ function setupHandle(socket, type, options) {
   const handle = new binding.Http2Session(type);
   handle[kOwner] = this;
 
-  if (typeof options.selectPadding === 'function')
-    this[kSelectPadding] = options.selectPadding;
   handle.consume(socket._handle);
   handle.ongracefulclosecomplete = this[kMaybeDestroy].bind(this, null);