docs(download): fix Arch Linux installation instructions (#24)

Author: casdal

download.html

@@ -82,9 +82,8 @@ <h3 id="linux-alt">ALT Linux</h3>
      class="btn btn-default" role="button">View ALT Linux packages</a>
 
   <h3 id="linux-arch">Arch Linux</h3>
-  <p>Arch Linux users can install <code>zeal</code> from AUR</p>
-  <a href="https://aur.archlinux.org/packages/zeal/"
-     class="btn btn-default" role="button">View zeal in AUR</a>
+  <p>Arch Linux users can either install Zeal from the community repository:</p>
+  <pre>$ sudo pacman -Syu zeal</pre>
   <p>Or use the <code>zeal-git</code> AUR package which builds unstable source code from our Git repository.</p>
   <a href="https://aur.archlinux.org/packages/zeal-git/"
      class="btn btn-default" role="button">View zeal-git in AUR</a>