godoc: move package example section

The example_html was being rendered outside the ".expanded" div which
did not hide it when the parent Overview div was being hidden. Moving it
inside the div so that the behavior is consistent

Fixes golang/go#23590

Change-Id: I75ee0af1c4074e02629b84ce366b34711e6d823b
Reviewed-on: https://go-review.googlesource.com/90396
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Andrew Bonventre <andybons@golang.org>

godoc/static/package.html

@@ -43,9 +43,9 @@
 			<div class="expanded">
 				<h2 class="toggleButton" title="Click to hide Overview section">Overview ▾</h2>
 				{{comment_html .Doc}}
+				{{example_html $ ""}}
 			</div>
 		</div>
-		{{example_html $ ""}}
 
 		<div id="pkg-index" class="toggleVisible">
 		<div class="collapsed">