Fix cast_test.cpp path

[SVN r8498]

libs/regression.cfg

@@ -27,7 +27,7 @@ compile-fail libs/static_assert/static_assert_test_fail_6.cpp
 compile-fail libs/static_assert/static_assert_test_fail_7.cpp
 compile-fail libs/static_assert/static_assert_test_fail_8.cpp
 compile libs/utility/call_traits_test.cpp
-run libs/cast_test.cpp
+run libs/utility/cast_test.cpp
 compile libs/utility/compressed_pair_test.cpp
 run libs/utility/iterator_adaptor_test.cpp
 run libs/utility/iterators_test.cpp