Bluetooth: tester: Disable forcing of MITM

Since some tests require MITM to be off, disable the option that forces
the MITM flag at all times.

Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
diff --git a/tests/bluetooth/tester/prj.conf b/tests/bluetooth/tester/prj.conf
index 51200c4..fb84bb6 100644
--- a/tests/bluetooth/tester/prj.conf
+++ b/tests/bluetooth/tester/prj.conf
@@ -7,6 +7,7 @@
 CONFIG_BT_PERIPHERAL=y
 CONFIG_BT_PRIVACY=n
 CONFIG_BT_SMP=y
+CONFIG_BT_SMP_ENFORCE_MITM=n
 CONFIG_BT_SIGNING=y
 CONFIG_BT_BONDABLE=y
 CONFIG_BT_ATT_PREPARE_COUNT=4