Test suite: cope with current actual behavior

As discussed on #18470, in some cases we use default bridges
when we could avoid it.

features/tor_bridges.feature

@@ -52,7 +52,8 @@ Feature: Using Tails with Tor bridges and pluggable transports
     Given the Tor network and default bridges are unblocked
     And I start "Tor Connection" via GNOME Activities Overview
     Then Tor is ready
-    And tca.conf includes no bridge
+    # XXX: When #18470 is resolved, uncomment the following step
+    #And tca.conf includes no bridge
     And available upgrades have been checked
     And all Internet traffic has only flowed through Tor