C++: Fix test failure.

Author: geoffw0

cpp/ql/test/query-tests/Security/CWE/CWE-190/semmle/tainted/ArithmeticTainted.expected

@@ -56,6 +56,7 @@ nodes
 | test.c:54:7:54:10 | len3 | semmle.label | len3 |
 | test.c:54:7:54:10 | len3 | semmle.label | len3 |
 | test.c:54:7:54:10 | len3 | semmle.label | len3 |
+subpaths
 #select
 | test2.cpp:14:11:14:11 | v | test2.cpp:25:22:25:23 | & ... | test2.cpp:14:11:14:11 | v | $@ flows to here and is used in arithmetic, potentially causing an overflow. | test2.cpp:25:22:25:23 | & ... | User-provided value |
 | test2.cpp:14:11:14:11 | v | test2.cpp:25:22:25:23 | & ... | test2.cpp:14:11:14:11 | v | $@ flows to here and is used in arithmetic, potentially causing an underflow. | test2.cpp:25:22:25:23 | & ... | User-provided value |