Fix logout url in doc

The default for logout is to redirect to `/login?logout`

Fixes gh-251

docs/manual/src/docs/asciidoc/index.adoc

@@ -664,7 +664,7 @@ URL `/logout` will log the user out by:
 - Invalidating the HTTP Session
 - Cleaning up any RememberMe authentication that was configured
 - Clearing the `SecurityContextHolder`
-- Redirect to `/login?success`
+- Redirect to `/login?logout`
 
 Similar to configuring login capabilities, however, you also have various options
 to further customize your logout requirements: