docs: fix typo
docs: fix typo

Signed-off-by: FUJITA Tomonori <93dac1fe9c4b2a3957982200319981492ad4976e@gmail.com>

osrg/gobgp,osrg/gobgp,a16/gobgp,a16/gobgp,j-kato/gobgp,fujita/gobgp,a16/gobgp,a16/gobgp,fujita/gobgp,a16/gobgp,a16/gobgp,a16/gobgp,j-kato/gobgp,osrg/gobgp,osrg/gobgp,j-kato/gobgp,fujita/gobgp,fujita/gobgp