Fix typo: <sting> -> <string>

Author: changeworld

articles/storage/common/redundancy-migration.md

@@ -149,7 +149,7 @@ To track the current migration status of the conversion initiated on your storag
 ```azurecli-interactive
 az storage account migration show \
     --account-name <string> \
-    - g <sting> \
+    - g <string> \
     -n "default"
 ```
 -->