Update URL for Japan NTP Page

[anthonypkeane]

Description

For ticket #15526
Please update the URL from https://brave.com/ja/users-bitflyer/ to https://brave.com/ja/desktop-ntp-tutorial

cc @Miyayes

[soham4abc]

@rebron @anthonypkeane Please review I have made a PR related to this issue. Please!

[rebron]

@anthonypkeane When is this page https://brave.com/ja/desktop-ntp-tutorial going live?

[stephendonner]

Verified PASSED using

Brave	1.26.73 Chromium: 91.0.4472.124 (Official Build) （x86_64）
変更履歴	7345a6d1bfcaff81162a957e9b7d52649fe2ac38-refs/branch-heads/4472_114@{#6}
OS	macOS バージョン11.4（ビルド20F71）

Steps:

1. set language + region in macOS to Japanese/Japan, respectively
2. new profile in Brave
3. launched Brave
4. looked at 2nd opened (but not focused) tab

Confirmed the URL in the 2nd tab is now https://brave.com/ja/desktop-ntp-tutorial/

---

Verified passed with

Brave	1.26.73 Chromium: 91.0.4472.124 (Official Build) （64 ビット）
変更履歴	7345a6d1bfcaff81162a957e9b7d52649fe2ac38-refs/branch-heads/4472_114@{#6}
OS	Linux

Confirmed on a clean profile that the 2nd tab (inactive) opened for Japan locale/language has the URL for https://brave.com/ja/desktop-ntp-tutorial/.

Also checked that on upgrade from 1.26.67 another tab with this URL is not opened.

---

Verification passed on

Brave	1.26.73 Chromium: 91.0.4472.124 (Official Build) （64 ビット）
変更履歴	7345a6d1bfcaff81162a957e9b7d52649fe2ac38-refs/branch-heads/4472_114@{#6}
OS	Windows 10 OS Version 1809 (Build 17763.1637)

Confirmed the URL in the 2nd tab is now https://brave.com/ja/desktop-ntp-tutorial/

Also checked that on upgrade from 1.26.67 another tab with this URL is not opened.