Change hardening level in std::span test

Fix rdar://134730449

Author: susmonteiro

test/Interop/Cxx/stdlib/use-std-span.swift

@@ -1,5 +1,5 @@
 // RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xcc -std=c++20)
-// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xcc -std=c++20 -Xcc -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST)
+// RUN: %target-run-simple-swift(-I %S/Inputs -Xfrontend -enable-experimental-cxx-interop -Xcc -std=c++20 -Xcc -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_DEBUG)
 
 // FIXME swift-ci linux tests do not support std::span
 // UNSUPPORTED: OS=linux-gnu