ash: Replace help center link for WebAuthn

A "Need help?" button in the WebAuthn dialog is supposed to link to
a help center article about WebAuthn. A placeholder link was put in
the code because we didn't have the dedicated p-link. Now that the
real p-link is created, use this instead.

This change needs to go into M88 to avoid confusion about the dialog.

Bug: b/177107168
Change-Id: I70e89cd2978a20221d02627a33113ce9c4cffd0d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2623628Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Yicheng Li <yichengli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842567}

chrome/browser/ui/ash/in_session_auth_dialog_client.cc

@@ -32,10 +32,8 @@ using chromeos::UserContext;
 
 namespace {
 
-// TODO(b/156258540): Replace with correct URL once the article is uploaded.
-// This URL is an irrelevant article just for validating functionality.
 const char kInSessionAuthHelpPageUrl[] =
-    "https://support.google.com/chrome/?p=settings_sign_in";
+    "https://support.google.com/chromebook?p=WebAuthn";
 
 InSessionAuthDialogClient* g_auth_dialog_client_instance = nullptr;