fix: add "Messages are end-to-end encrypted." to non-protected groups

The messages are end-to-end encrypted
in encrypted group regardless
of whether the group is protected or not.

python/tests/test_3_offline.py

@@ -663,4 +663,4 @@ class TestOfflineChat:
 
         lp.sec("check message count of only system messages (without daymarkers)")
         sysmessages = [x for x in chat.get_messages() if x.is_system_message()]
-        assert len(sysmessages) == 3
+        assert len(sysmessages) == 4