Windows: Clarify r/o root filesystem
Windows: Clarify r/o root filesystem

Signed-off-by: John Howard <50ae662f5fcde39b7d1ed786133b7c61a25411dd@microsoft.com>

opencontainers/runtime-spec,wking/opencontainer-runtime-spec,hqhq/specs,wking/opencontainer-specs,opencontainers/specs,hqhq/runtime-spec,laijs/specs