docs: update document for policy-related commands
docs: update document for policy-related commands

Signed-off-by: ISHIDA Wataru <15703620d0b11e835ab4f34ebf88f2f40cce783e@lab.ntt.co.jp>

a16/gobgp,osrg/gobgp,Dipsingh/gobgp,a16/gobgp,j-kato/gobgp,a16/gobgp,fujita/gobgp,a16/gobgp,h-naoto/gobgp,Dipsingh/gobgp,osrg/gobgp,fujita/gobgp,a16/gobgp,ishidawataru/gobgp,tamihiro/gobgp,Dipsingh/gobgp,tamihiro/gobgp,tamihiro/gobgp,ramrunner/gobgp,ramrunner/gobgp,osrg/gobgp,ishidawataru/gobgp,ramrunner/gobgp,tamihiro/gobgp,YujiOshima/gobgp,h-naoto/gobgp,fujita/gobgp,YujiOshima/gobgp,a16/gobgp,fujita/gobgp,h-naoto/gobgp,j-kato/gobgp,ishidawataru/gobgp,j-kato/gobgp,a16/gobgp,osrg/gobgp,YujiOshima/gobgp