Update PSAzureActiveDirectoryApp so that TenantId can be updated (#13220)

Update PSAzureActiveDirectoryApp so that TenantId can be updated.
By default, the cmdlet sets TenantId from the logged in context, but customer may want to provide a different tenantid.

Author: hitenjava

src/DataMigration/DataMigration/Models/PSAzureActiveDirectoryApp.cs

@@ -33,7 +33,7 @@ public PSAzureActiveDirectoryApp(string tenantId)
 
         public SecureString AppKey { get; set; }
 
-        public string TenantId { get; private set; }
+        public string TenantId { get; set; }
 
     }
-}
+}