spec: clarify when a range expression is evaluated

If the range expression is a numeric constant, the
range expression is also not evaluated.

Change-Id: I97201e5c136d3d1a87ed1500b19b7199b30bc9ff
Reviewed-on: https://go-review.googlesource.com/c/go/+/581298
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Bypass: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>

doc/go_spec.html

@@ -1,6 +1,6 @@
 <!--{
 	"Title": "The Go Programming Language Specification",
-	"Subtitle": "Language version go1.22 (Feb 6, 2024)",
+	"Subtitle": "Language version go1.22 (April 24, 2024)",
 	"Path": "/ref/spec"
 }-->
 
@@ -6644,8 +6644,8 @@ <h4 id="For_range">For statements with <code>range</code> clause</h4>
 
 <p>
 The range expression <code>x</code> is evaluated once before beginning the loop,
-with one exception: if at most one iteration variable is present and
-<code>len(x)</code> is <a href="#Length_and_capacity">constant</a>,
+with one exception: if at most one iteration variable is present and <code>x</code> or
+<a href="#Length_and_capacity"><code>len(x)</code></a> is <a href="#Constants">constant</a>,
 the range expression is not evaluated.
 </p>