spec: delete incorrect obsolete mention of selector working on

pointer to interface type.

R=golang-dev, niemeyer, gri
CC=golang-dev
https://golang.org/cl/4173067

doc/go_spec.html

 <!-- title The Go Programming Language Specification -->
-<!-- subtitle Version of February 15, 2011 -->
+<!-- subtitle Version of February 19, 2011 -->
 
 <!--
 TODO
@@ -2267,7 +2267,7 @@ If there is not exactly one <code>f</code> with shallowest depth, the selector
 expression is illegal.
 </li>
 <li>
-For a variable <code>x</code> of type <code>I</code> or <code>*I</code>
+For a variable <code>x</code> of type <code>I</code>
 where <code>I</code> is an interface type,
 <code>x.f</code> denotes the actual method with name <code>f</code> of the value assigned
 to <code>x</code> if there is such a method.