Update reference to Fetch Standard step number (#173)

index.src.html

@@ -653,7 +653,7 @@ <h2 id="integration-with-fetch">Integration with Fetch</h2>
 
   The Fetch specification calls out to
   [[#set-requests-referrer-policy-on-redirect]]
-  before [[fetch#http-redirect-fetch|Step 13 of the HTTP-redirect fetch]], so
+  before [[fetch#http-redirect-fetch|Step 19 of the HTTP-redirect fetch]], so
   that a request's referrer policy can be updated before following a redirect.
 
   The Fetch specification calls out to [[#determine-requests-referrer]]