tests: use correct kconfig in help message

CONFIG_TEST_HAS_USERSPACE was removed, fix the help the text to reflect
that.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/subsys/testsuite/Kconfig b/subsys/testsuite/Kconfig
index 7429cab..51c4551 100644
--- a/subsys/testsuite/Kconfig
+++ b/subsys/testsuite/Kconfig
@@ -84,7 +84,7 @@
 	  This hidden option will help test the userspace mode. This will be
 	  enabled only when CONFIG_ARCH_HAS_USERSPACE is set, and that the test
 	  case itself indicates that it exercises user mode via
-	  CONFIG_TEST_HAS_USERSPACE.
+	  CONFIG_TEST_USERSPACE.
 
 config TEST_HW_STACK_PROTECTION
 	bool "Enable hardware-based stack overflow detection if available"