Display correct runtime-spec version
Display correct runtime-spec version

Instead of using a constant as the runtime-spec
version, user `Version` in the package.

Signed-off-by: Lei Jitang <9ac444d2b5df3db1f31aa1c6462ac8e9e2bde241@huawei.com>

opencontainers/image-tools,xiekeyang/image-tools,xiekeyang/image-tools,opencontainers/image-tools