spec: remove note re: field accesses on type literals

For #51576.

Change-Id: I43f72c3fb618e724d46360a70ab9f8abc3d63273
Reviewed-on: https://go-review.googlesource.com/c/go/+/391137
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go_spec.html

@@ -3289,10 +3289,6 @@ <h3 id="Primary_expressions">Primary expressions</h3>
 
 <h3 id="Selectors">Selectors</h3>
 
-<p><b>
-[This section is missing rules for x.f where x's type is a type parameter and f is a field.]
-</b></p>
-
 <p>
 For a <a href="#Primary_expressions">primary expression</a> <code>x</code>
 that is not a <a href="#Package_clause">package name</a>, the