The --tcp-close option was introduced with commit

2c370428
tcp: Add tcp-close option to restore connected TCP sockets in closed state

This options is applicable only for restore. Therefore, move the
documentation from 'dump' to 'restore'.
Signed-off-by: Radostin Stoyanov <rstoyanov1@gmail.com>
Signed-off-by: Andrei Vagin <avagin@gmail.com>