fixed the TOC link

Author: alkohli

articles/databox/TOC.yml

@@ -162,7 +162,7 @@
       - name: Migrate
         items:
         - name: To SharePoint Online
-          href: data-box-heavy-migrate-spo
+          href: data-box-heavy-migrate-spo.md
         - name: To Azure File Sync
           href: ../storage/files/storage-sync-offline-data-transfer.md?toc=/azure/databox/toc.json&bc=/azure/databox/breadcrumb/toc.json
         - name: From HDFS store