DEX draft: Checksum Complement bit

[talmi]

The following text in the draft should be reconsidered. There may be scenarios in which the Checksum Complement is necessary.

               bit 23, which corresponds to the Checksum Complement
               data field, should be assigned to be zero by the IOAM
               encapsulating node, and ignored by transit and
               decapsulating nodes.  The reason for this is that the
               Checksum Complement is intended for in-flight packet
               modifications and is not relevant for direct
               exporting.