backupccl: use correct version gate for restore checkpointing

PR #97862 introduced a subtle bug which allowed the new restore checkpointing
policy to take effect before the 23_1 migrations occured. This patch ensures
the new policy only takes effect after all migrations occur.

Release note: None

Epic: None

pkg/ccl/backupccl/backup_test.go

@@ -1811,7 +1811,7 @@ func TestBackupRestoreResume(t *testing.T) {
 				},
 			},
 			// Required because restore checkpointing is version gated.
-			clusterversion.ByKey(clusterversion.V23_1Start),
+			clusterversion.ByKey(clusterversion.V23_1),
 		)
 		// If the restore properly took the (incorrect) low-water mark into account,
 		// the first half of the table will be missing.

pkg/ccl/backupccl/restore_job.go

@@ -287,7 +287,7 @@ func restore(
 		return emptyRowCount, err
 	}
 
-	on231 := clusterversion.ByKey(clusterversion.V23_1Start).LessEq(job.Payload().CreationClusterVersion)
+	on231 := clusterversion.ByKey(clusterversion.V23_1).LessEq(job.Payload().CreationClusterVersion)
 	progressTracker, err := makeProgressTracker(
 		dataToRestore.getSpans(),
 		job.Progress().Details.(*jobspb.Progress_Restore).Restore.Checkpoint,