1:6.6p1-2ubuntu2.10) is not available, but a newer one is (1:6.6p1-2ubuntu2.13). We redirected you there.
/usr/share/doc/openssh-server is in openssh-server 1:6.6p1-2ubuntu2.13.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/openssh-client