Set-AzExpressRoutePort: `-ExpressRoutePort` expects un-documented type

## Description

In the [document](https://docs.microsoft.com/en-us/powershell/module/az.network/set-azexpressrouteport?view=azps-5.4.0) `Set-AzExpressRoutePort -ExpressRoutePort` expects type `Microsoft.Azure.Commands.Network.Models.PSExpressRoutePort` whilst in fact it requires `Microsoft.Azure.Management.Network.Models.ExpressRoutePort`.

## Steps to reproduce

```powershell
$erport = Get-AzExpressRoutePort -Name $PortName -ResourceGroupName $rg
Set-AzExpressRoutePort -ExpressRoutePort $erport
```

## Module versions

```powershell
4.5.0 Az.Network
```

## Error output

```
Set-AzExpressRoutePort: Error mapping types.
Mapping types:
PSExpressRoutePort -> ExpressRoutePort
Microsoft.Azure.Commands.Network.Models.PSExpressRoutePort -> Microsoft.Azure.Management.Network.Models.ExpressRoutePort
Type Map configuration:
PSExpressRoutePort -> ExpressRoutePort
Microsoft.Azure.Commands.Network.Models.PSExpressRoutePort -> Microsoft.Azure.Management.Network.Models.ExpressRoutePort
Property:
Links
```

Start with the Set-AzExpressRoutePort documentation linked in the issue and reproduce the commands using Get-AzExpressRoutePort and Set-AzExpressRoutePort. Compare the documented -ExpressRoutePort type with the type required by the cmdlet; done means the documentation and the reported command behavior agree without the mapping error.

Written by the indexing model from the issue text.