doc: fix grammar in go1.8.html > crypto/tls

Change-Id: If8200e54b3650f789c5312f10cce32201a199b80
Reviewed-on: https://go-review.googlesource.com/33775Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

doc/go1.8.html

@@ -766,7 +766,7 @@ Optimizations and bug fixes are not listed.
       X25519 and <!-- CL 30824, CL 30825 -->
       ChaCha20-Poly1305.  <!-- CL 30957, CL 30958 -->
       ChaCha20-Poly1305 is now prioritized unless <!-- CL 32871 -->
-      AES-GCM when hardware support is present.
+      hardware support for AES-GCM is present.
     </p>
 
     <p> <!-- CL 27315 -->