Update expressroute-howto-gateway-migration-portal.md

update time in prepare

Author: MekaylaMoore

articles/expressroute/expressroute-howto-gateway-migration-portal.md

@@ -56,7 +56,7 @@ Here are the steps to migrate to a new gateway in Azure portal.
     > [!NOTE]
     > Be aware that your existing Virtual Network gateway will be locked during this process, preventing any creation or modification of connections to this gateway.
 
-1. Select **Prepare** to create the new gateway. This operation could take up to 15 minutes.
+1. Select **Prepare** to create the new gateway. This operation could take up to 60 minutes.
 
 1. After the new gateway is created, you'll proceed to the *Migrate* stage. Here, select the new gateway you created. In this example, it's **myERGateway_migrated**. This transfers the settings from your old gateway to the new one. All network traffic, control plane, and data path connections from your old gateway will transfer without any interruptions. To start this process, select **Migrate Traffic**. This operation could take up to 5 minutes.