fix: no need to flush ofstream every time

Author: hyj1991

src/logger.cc

@@ -25,7 +25,6 @@ using v8::String;
   uv_mutex_lock(&logger_mutex);                \
   type##_stream.open(filepath, std::ios::app); \
   type##_stream << log;                        \
-  type##_stream.flush();                       \
   type##_stream.close();                       \
   uv_mutex_unlock(&logger_mutex);