migration: Remove unused socket_send_channel_create_sync

socket_send_channel_create_sync only use was removed by
  d0edb8a173 ("migration: Create the postcopy preempt channel asynchronously")

Remove it.

Signed-off-by: Dr. David Alan Gilbert <dave@treblig.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Link: https://lore.kernel.org/r/20240919134626.166183-5-dave@treblig.org
Signed-off-by: Peter Xu <peterx@redhat.com>
2 files changed