`recoveryservicesbackup`: `ProtectedItems_CreateOrUpdate` lacks `x-ms-long-running-operation`

It's an async operation per the description, so for the action [`ProtectedItems_CreateOrUpdate`](https://github.com/Azure/azure-rest-api-specs/blob/main/specification/recoveryservicesbackup/resource-manager/Microsoft.RecoveryServices/stable/2023-01-01/bms.json#L1378), it should be marked with `"x-ms-long-running-operation": true,` like [this](https://github.com/Azure/azure-rest-api-specs/blob/main/specification/recoveryservicessiterecovery/resource-manager/Microsoft.RecoveryServices/stable/2022-10-01/service.json#L4733)

Open specification/recoveryservicesbackup/resource-manager/Microsoft.RecoveryServices/stable/2023-01-01/bms.json and locate ProtectedItems_CreateOrUpdate around line 1378. Compare its operation metadata with the referenced service.json example around line 4733, then add the missing long-running-operation declaration and verify the specification diff.

Written by the indexing model from the issue text.