fix typo in nosniff header documentation

The option is "nosniff", not "no sniff".

Review URL: https://chromiumcodereview.appspot.com/11145034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@162457 0039d316-1c4b-4281-b951-d872f2087c98

chrome/common/extensions/docs/templates/articles/hosting.html

@@ -74,7 +74,7 @@ if <b>either</b> of the following is true:
 <p>
 The most common reason for failing to recognize an installable file
 is that the server sends the header
-<code>X-Content-Type-Options: no sniff</code>.
+<code>X-Content-Type-Options: nosniff</code>.
 The second most common reason
 is that the server sends an unknown content type&mdash;one
 that isn't in the previous list.