Fix typos in fs/fs.go
Fix typos in fs/fs.go

Signed-off-by: Zuti He <ec2668e0ad32034c5df2087563fb5a5914e5bd28@gmail.com>

containerd/stargz-snapshotter,containerd/stargz-snapshotter,containerd/stargz-snapshotter,containerd/stargz-snapshotter