decom: avoid skipping single delete markers for replication (#20836)

It is possible delete marker was received on old pool as decom
move in progress, this PR allows decom retry to ensure these
delete markers are moved to new pool so that decommission can
be completed.

Fixes #20819

cmd/erasure-server-pool-decom.go

@@ -845,7 +845,7 @@ func (z *erasureServerPools) decommissionPool(ctx context.Context, idx int, pool
 				// to decommission, just skip it, this also includes
 				// any other versions that have already expired.
 				remainingVersions := len(fivs.Versions) - expired
-				if version.Deleted && remainingVersions == 1 {
+				if version.Deleted && remainingVersions == 1 && rcfg == nil {
 					decommissioned++
 					stopFn(version.Size, errors.New("DELETE marked object with no other non-current versions will be skipped"))
 					continue