[libc++] NFC: Simplify incude of <cstdlib>

We include <exception>, which includes <cstdlib> unconditionally anyway.

GitOrigin-RevId: 69ca17a92c20b3c01d55ea31331580625f37c168
diff --git a/include/stdexcept b/include/stdexcept
index 7a7f367..7b5de7e 100644
--- a/include/stdexcept
+++ b/include/stdexcept
@@ -42,11 +42,9 @@
 */
 
 #include <__config>
+#include <cstdlib>
 #include <exception>
 #include <iosfwd>  // for string forward decl
-#ifdef _LIBCPP_NO_EXCEPTIONS
-#include <cstdlib>
-#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header