Remove unused macro

include/rapidjson/writer.h

@@ -231,7 +231,6 @@ protected:
             os_->Put(*p);
         return true;
     }
-#undef RAPIDJSON_SNPRINTF
 
     bool WriteString(const Ch* str, SizeType length)  {
         static const char hexDigits[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };