rm recently EOL'd enhanced 404 js

Test failed in CI, found more info at tofuconf/tofuconf.club#179 (comment)

Author: mlinksva

404.md

@@ -6,9 +6,3 @@ title: Not found
 <p class="text-center alt-lead">
   The page you're looking for doesn't seem to be there!
 </p>
-
-<script>
-  var GOOG_FIXURL_LANG = "en";
-  var GOOG_FIXURL_SITE = "{{ site.url }}";
-</script>
-<script src="//linkhelp.clients.google.com/tbproxy/lh/wm/fixurl.js"></script>