docs: netdev: recommend against --in-reply-to

It's somewhat unfortunate but with (my?) the current tooling
if people post new versions of a set in reply to an old version
managing the review queue gets difficult. So recommend against it.

Reviewed-by: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://lore.kernel.org/r/20230823154922.1162644-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>