doc/go1.11: fix bad link to Int.ModInverse

Change-Id: I659bc5b61dade9438b122e6994da022946f5e1d3
Reviewed-on: https://go-review.googlesource.com/125255Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.11.html

@@ -550,7 +550,7 @@ for k := range m {
   <dd>
 
     <p><!-- CL 108996 -->
-      <a href="/pkg/math/bin/#Int.ModInverse"><code>ModInverse</code></a> now returns nil when g and n are not relatively prime. The result was previously undefined.
+      <a href="/pkg/math/big/#Int.ModInverse"><code>ModInverse</code></a> now returns nil when g and n are not relatively prime. The result was previously undefined.
     </p>
 
 </dl><!-- math/big -->