Mark the "Tor Browser shows the [...] error" step as fragile.

Refs: #11591

features/torified_browsing.feature

@@ -4,6 +4,8 @@ Feature: Browsing the web using the Tor Browser
   when I browse the web using the Tor Browser
   all Internet traffic should flow only through Tor
 
+  #11591
+  @fragile
   Scenario: The Tor Browser cannot access the LAN
     Given I have started Tails from DVD and logged in and the network is connected
     And a web server is running on the LAN