Revert "netfilter: conntrack: add sctp DATA_SENT state"

This reverts commit (bff3d053

: "netfilter: conntrack: add sctp
DATA_SENT state")

Using DATA/SACK to detect a new connection on secondary/alternate paths
works only on new connections, while a HEARTBEAT is required on
connection re-use. It is probably consistent to wait for HEARTBEAT to
create a secondary connection in conntrack.

Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>