message: docs: update changelog link
diff: ### Tips
  -The current document is the changelog of Vant 3. If you want to view the changelog of Vant 2, please visit [Vant 2 Changelog](https://youzan.github.io/vant/#/en-US/changelog).
  +The current document is the changelog of Vant 3. If you want to view the changelog of Vant 2, please visit [Vant 2 Changelog](https://youzan.github.io/vant/v2/#/en-US/changelog).
  ### Intro
  