update docs to match new Facebook UI (aws-amplify#4707)

Author: tjleing

src/fragments/lib/auth/common/social_signin_web_ui/configure_auth_category.mdx

@@ -24,7 +24,7 @@ You need to now inform your auth provider of this URL:
 
     ![Image](/images/cognitoHostedUI/facebook6.png)
 8. Save changes.
-9. From the navigation bar choose *Products* and then *Set up* from *Facebook Login*.
+9. From the navigation bar choose *Add Product* and then *Set up* from *Facebook Login*.
 ![Image](/images/cognitoHostedUI/facebook7.png)
 10. From the navigation bar choose *Facebook Login* and then *Settings*.
 11. Type your redirect URL into *Valid OAuth Redirect URIs*. It will consist of your user pool domain with the /oauth2/idpresponse endpoint.