godoc/dl: remove the tiny, unselectable SHA sums from Featured Downloads

The SHA sums are clearly visible (and copy-pastable) in the expanded section
immediately below it.

Fixes golang/go#16900.

Change-Id: If1805534b3893f6c38f4170c4b457ff0e935ce28
Reviewed-on: https://go-review.googlesource.com/33290
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

godoc/dl/tmpl.go

@@ -258,7 +258,6 @@ $(document).ready(function() {
   <span class="filename">{{.Filename}}</span>
   {{if .Size}}<span class="size">({{.PrettySize}})</span>{{end}}
 </div>
-<div class="checksum">{{.ChecksumType}}: {{.PrettyChecksum}}</div>
 </a>
 {{end}}
 `