Add hyphen for host specific
Add hyphen for host specific

We have `host-specific` and `host specific` in the same doc,
add hyphen to keep consistency.

Signed-off-by: Qiang Huang <488e06933c295c76472a67dbc6657ac40a756953@huawei.com>

cloudfoundry-incubator/specs,laijs/specs,opencontainers/specs,hqhq/runtime-spec,wking/opencontainer-specs,jonboulle/specs,vbatts/specs,hqhq/specs,gao-feng/specs,ujuc/specs,opencontainers/runtime-spec,wking/opencontainer-runtime-spec