doc/go1.7: fix typo in nsswitch.conf name

Fixes #15939

Change-Id: I120cbeac73a052fb3f328774e6d5e1534f11bf6b
Reviewed-on: https://go-review.googlesource.com/23682Reviewed-by: Ian Lance Taylor <iant@golang.org>

doc/go1.7.html

@@ -795,7 +795,7 @@ Go 1.7 adds the hexadecimal encoding of the bytes, as in <code>"?12ab"</code>.
 
 <p>
 The pure Go <a href="/pkg/net/#hdr-Name_Resolution">name resolution</a>
-implementation now respects <code>nsswtch.conf</code>'s
+implementation now respects <code>nsswitch.conf</code>'s
 stated preference for the priority of DNS lookups compared to
 local file (that is, <code>/etc/hosts</code>) lookups.
 </p>