[libc++] Quick fix to remove a narrowing conversion from the in_out_result test.

[var-const]

Summary

This needs a proper solution in a follow-up. The issue is that the
Standard defines conversions between in_out_result classes with
different template types as just return {in, out};. Because the
expression uses list initialization, it will fail to compile if the
conversion happens to be narrowing -- which is probably unintended.

Surprisingly, this error wasn't caught by the CI.

libcxx/test/std/algorithms/algorithms.results/in_out_result.pass.cpp

 
 #endif // __Fuchsia__
 
 int main(int, char**) {
 #ifndef __Fuchsia__
   // Conversion, fundamental types.
   {
     std::ranges::in_out_result<int, bool> x = {2, false};
-    std::ranges::in_out_result<double, char> y = x;
-    assert(y.in == 2.0);
+    // FIXME(varconst): try a narrowing conversion.
+    std::ranges::in_out_result<long, char> y = x;
+    assert(y.in == 2);
     assert(y.out == '\0');
   }
 
   // Conversion, user-defined types.
   {
     struct From1 {
       int value = 0;
       From1(int v) : value(v) {}
// Unsuccessful conversion.
     struct Bar2 {};
     static_assert(
         !std::is_convertible_v<std::ranges::in_out_result<Foo1, Foo2>, std::ranges::in_out_result<Bar1, Bar2>>);
   }
 #endif // __Fuchsia__
 
   return 0;
 }
-