adding backup/offline-backup-azure-data-box to databox toc

Author: priestlg

articles/databox/TOC.yml

@@ -70,6 +70,8 @@
           href: ../storage/files/storage-sync-offline-data-transfer.md?toc=/azure/databox/toc.json&bc=/azure/databox/breadcrumb/toc.json
         - name: From HDFS store
           href: ../storage/blobs/data-lake-storage-migrate-on-premises-hdfs-cluster.md?toc=/azure/databox/toc.json&bc=/azure/databox/breadcrumb/toc.json 
+        - name: From HDFS store
+          href: ../backup/offline-backup-azure-data-box.md?toc=/azure/databox/toc.json&bc=/azure/databox/breadcrumb/toc.json 
       - name: Troubleshoot
         items:
         - name: Data Box issues