playground: update snippet to tell version

The previous snippet was created almost 4 years ago in CL 2308. Update
to a more modern snippet (created today) for the following reasons:

• Apply gofmt (previous one was missing a newline at EOF).
• It uses the current ID generation scheme, making it possible
  to re-create the same snippet in another playground instance.

Change-Id: I50157f9a8d313f3c826d4289c91c42049ac5bd0d
Reviewed-on: https://go-review.googlesource.com/c/149341
Reviewed-by: Brad Fitzpatrick <[email protected]>

Author: dmitshur

edit.html

@@ -180,7 +180,7 @@
 
 <p>
 The playground uses the latest stable release of Go.<br>
-The current version is <a href="/p/1VcPUlPk_3">{{.GoVersion}}</a>.
+The current version is <a href="/p/Ztyu2FJaajl">{{.GoVersion}}</a>.
 </p>
 
 <p>