fixup! [libc][math][c23] Add f16subf C23 math function

Fix conversion to output type.

Author: overmighty

libc/src/__support/FPUtil/dyadic_float.h

@@ -156,13 +156,13 @@ template <size_t Bits> struct DyadicFloat {
       // d_lo is denormal, but the output is normal.
       int scale_up_exponent = 1 - exp_lo;
       T scale_up_factor =
-          FPBits<T>::create_value(sign,
+          FPBits<T>::create_value(Sign::POS,
                                   static_cast<output_bits_t>(
                                       FPBits<T>::EXP_BIAS + scale_up_exponent),
                                   IMPLICIT_MASK)
               .get_val();
       T scale_down_factor =
-          FPBits<T>::create_value(sign,
+          FPBits<T>::create_value(Sign::POS,
                                   static_cast<output_bits_t>(
                                       FPBits<T>::EXP_BIAS - scale_up_exponent),
                                   IMPLICIT_MASK)