tests: bluetooth: tester: workaround build error

For mysterious reasons this test fails cmake if
CONFIG_TEST_USERSPACE=n.

Enable it for now, bug tracked in #15232

Signed-off-by: Andrew Boie <[email protected]>

Author: Andrew Boie

tests/bluetooth/tester/default.conf

@@ -34,3 +34,6 @@ CONFIG_BT_TESTING=y
 
 CONFIG_UART_CONSOLE=n
 CONFIG_GPIO=y
+
+# FIXME: #15232
+CONFIG_TEST_USERSPACE=y