Remove the prerelease notice from the website

Author: jgonggrijp

index.html

@@ -449,15 +449,6 @@
       >the article</a>.
     </p>
 
-    <p>
-      <i>Prerelease version 1.13.0-1 adds full support for native ESM imports
-      in Node.js version 12 and later. It should do this without breaking
-      existing setups. Please try it out by installing
-      <tt>underscore@preview</tt> from NPM and let us know whether it worked
-      for you in <a href="https://github.com/jashkenas/underscore/pull/2914">the
-      pull request</a>!</i>
-    </p>
-
     <p>
       Enjoying Underscore, and want to <i>turn it up to 11?</i> Try <a href="https://documentcloud.github.io/underscore-contrib/">Underscore-contrib</a>.
     </p>