Consolidate restore article

Author: kevinvngo

articles/sql-data-warehouse/TOC.yml

@@ -213,12 +213,8 @@
     items:
     - name: Monitor your workload
       href: sql-data-warehouse-manage-monitor.md
-    - name: Restore - Portal
-      href: sql-data-warehouse-restore-database-portal.md
-    - name: Restore - PowerShell
-      href: sql-data-warehouse-restore-database-powershell.md
-    - name: Restore - REST API
-      href: sql-data-warehouse-restore-database-rest-api.md
+    - name: Restore your data warehouse
+      href: sql-data-warehouse-restore.md
     - name: Upgrade to Gen2
       href: upgrade-to-latest-generation.md
     - name: Automate performance levels