doc: remove deprecated alpha1 reference of snapshot objects
doc: remove deprecated alpha1 reference of snapshot objects

alpha1 version is deprecated and this commit correct the
example doc and make it GAd version

Additional note: we have already moved the artifacts to v1 version.

Signed-off-by: Humble Chirammal <dc8ba7e82a7df22725dedec9b10c7aaab9ec713f@redhat.com>

ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi,ceph/ceph-csi