spec: update operator and delimiter section

Follow-up on https://go-review.googlesource.com/30601.

Change-Id: I51b603a6c4877b571e83cd7c4e78a8988cc831ca
Reviewed-on: https://go-review.googlesource.com/32310Reviewed-by: Rob Pike <r@golang.org>

doc/go_spec.html

 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Version of October 27, 2016",
+	"Subtitle": "Version of October 28, 2016",
 	"Path": "/ref/spec"
 }-->
 
@@ -265,7 +265,7 @@ The following character sequences represent <a href="#Operators">operators</a>,
 *    ^     *=    ^=     &lt;-    &gt;     &gt;=    {    }
 /    &lt;&lt;    /=    &lt;&lt;=    ++    =     :=    ,    ;
 %    &gt;&gt;    %=    &gt;&gt;=    --    !     ...   .    :
-     &amp;^          &amp;^=
+     &amp;^          &amp;^=    =&gt;
 </pre>
 
 <h3 id="Integer_literals">Integer literals</h3>