message: Remove NODISCARD
diff: #ifndef BITCOIN_ATTRIBUTES_H
  #define BITCOIN_ATTRIBUTES_H
  -#if defined(__has_cpp_attribute)
  -# if __has_cpp_attribute(nodiscard)
  -# define NODISCARD [[nodiscard]]
  -# endif
  -#endif
  -#ifndef NODISCARD
  -# if defined(_MSC_VER) && _MSC_VER >= 1700
  -# define NODISCARD _Check_return_
  -# else
  -# define NODISCARD __attribute__((warn_unused_result))
  -# endif
  -#endif
  -
  #if defined(__clang__)
  # if __has_attribute(lifetimebound)
  # define LIFETIMEBOUND [[clang::lifetimebound]]
  