Fix `5.1.0` link on home page

[ShubhamOulkar]

Never got updated after this commit c8e36fc.

fix: Remove 4x.html from the link.

<div class="express">
  <a href="/">Express</a>
  <a href="{{ page.lang }}/changelog/4x.html#{{ site.data.express.current_version }}" id="express-      version">{{ site.data.express.current_version }}</a>
</div>

Note: Also need to fix Express link. It is not right. We are on home page so dont need to link itself. Also we have two home links in top navigation bar. (logo and home link)