fix(steps-guix): enable CONFIG_USER_NS in kernel config

Author: vxtls

steps-guix/linux-6.12.74/files/config.txt

@@ -210,7 +210,7 @@ CONFIG_NAMESPACES=y
 CONFIG_UTS_NS=y
 CONFIG_TIME_NS=y
 CONFIG_IPC_NS=y
-# CONFIG_USER_NS is not set
+CONFIG_USER_NS=y
 CONFIG_PID_NS=y
 CONFIG_NET_NS=y
 # CONFIG_CHECKPOINT_RESTORE is not set