Get-AzAutomationSoftwareUpdateConfiguration returns a wrong value for the OperatingSystem property

### Description

Scheduled update deployments in Azure Automation Update Management are set up for Linux operating system and the Portal shows the correct data ("Linux").

Get-AzAutomationSoftwareUpdateConfiguration returns the incorrect value "Windows" for the OperatingSystem property.

### Module Version

```powershell
Get-Module Az.Automation -ListAvailable
ModuleType Version Name
---------- ------- ----
Script 1.0.0 Az.Automation
```

### Environment Data

```powershell
PS C:\> $PSVersionTable

Name Value
---- -----
PSVersion 6.1.1
PSEdition Core
GitCommitId 6.1.1
OS Microsoft Windows 10.0.17763
Platform Win32NT
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0...}
PSRemotingProtocolVersion 2.3
SerializationVersion 1.1.0.1
WSManStackVersion 3.0
```

### Debug Output

```

```