message: refine a comment per Tatiana's suggestions
diff: @@ -2098,7 +2098,7 @@ static inline memory::format get_desired_format(int channel,
  (channel % 8) == 0) {
  fmt_desired = is_2d
  ? memory::format::nChw8c
  - : memory::format::ncdhw; // not support avx2 for 3d yet.
  + : memory::format::ncdhw; // no avx2 support for 3d yet.
  } else {
  fmt_desired = is_2d ? memory::format::nchw : memory::format::ncdhw;
  }
  