Fix unused variable warning

Author: mborland

include/boost/decimal/decimal64_t.hpp

@@ -1921,8 +1921,7 @@ constexpr auto operator/(const Integer lhs, const decimal64_t rhs) noexcept
     #ifndef BOOST_DECIMAL_FAST_MATH
     // Check pre-conditions
     constexpr decimal64_t zero {0, 0};
-    constexpr decimal64_t inf {boost::decimal::from_bits(boost::decimal::detail::d64_inf_mask)};
-    constexpr decimal64_t nan {boost::decimal::from_bits(boost::decimal::detail::d64_snan_mask)};
+    constexpr decimal64_t inf {from_bits(detail::d64_inf_mask)};
 
     const auto rhs_fp {fpclassify(rhs)};