Gemfile: bump gh-pages to v177
Gemfile: bump gh-pages to v177

To be inline with https://github.com/docker/docker.github.io/pull/6153
and https://github.com/docker/docker.github.io/pull/6159.

Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

JimGalasyn/docker.github.io,anweiss/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,JimGalasyn/docker.github.io,anweiss/docker.github.io,docker/docker.github.io,anweiss/docker.github.io,thaJeztah/docker.github.io,JimGalasyn/docker.github.io,londoncalling/docker.github.io,JimGalasyn/docker.github.io,thaJeztah/docker.github.io,JimGalasyn/docker.github.io,londoncalling/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,johnstep/docker.github.io,londoncalling/docker.github.io,docker/docker.github.io,johnstep/docker.github.io,anweiss/docker.github.io,anweiss/docker.github.io,johnstep/docker.github.io,johnstep/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,johnstep/docker.github.io,londoncalling/docker.github.io,londoncalling/docker.github.io