enable null cipher heuristic by default in config

Author: cooperq

dist/config.toml.example

@@ -28,4 +28,4 @@ key_input_mode = 0
 imsi_requested = true
 connection_redirect_2g_downgrade = true
 lte_sib6_and_7_downgrade = true
-null_cipher = false
+null_cipher = true