[doc] struct: update note about network byte order form to be more helpful (GH-22201)


Update the sentence to provide some context on why network byte order is defined as big endian.
(cherry picked from commit fb2718720346c8c7a0ad2d7477f20e9a5524ea0c)

Co-authored-by: Stargirl Flowers <theaflowers@google.com>
1 file changed