manifest.go:remove the size of the layers of judgment
manifest.go:remove the size of the layers of judgment

Signed-off-by: zhouhao <f577ade201aa03d612c19915a089dc6084d45cd9@cn.fujitsu.com>

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