Update - Update deployment (external VNET) (#15391)

Update deployment (external VNET)  -- Location parameter is creating an error
The location parameter was creating an issue when I tried to integrate my APIM with Internal Vnet>
I had the following error:
New-AzApiManagementVirtualNetwork: A parameter cannot be foundthat matches parameter name 'Location'.
However, removing the -Location parameter worked for me.

Author: mikemej

src/ApiManagement/ApiManagement/help/Set-AzApiManagement.md

@@ -36,7 +36,7 @@ This example gets an Api Management instance, scales it to five premium units an
 
 ### Example 2: Update deployment (external VNET)
 ```powershell
-PS C:\> $virtualNetwork = New-AzApiManagementVirtualNetwork -Location "East US" -SubnetResourceId "/subscriptions/a8ff56dc-3bc7-4174-a1e8-3726ab15d0e2/resourceGroups/Api-Default-WestUS/providers/Microsoft.Network/virtualNetworks/dfVirtualNetwork/subnets/backendSubnet"
+PS C:\> $virtualNetwork = New-AzApiManagementVirtualNetwork -SubnetResourceId "/subscriptions/a8ff56dc-3bc7-4174-a1e8-3726ab15d0e2/resourceGroups/Api-Default-WestUS/providers/Microsoft.Network/virtualNetworks/dfVirtualNetwork/subnets/backendSubnet"
 PS C:\> $apim = Get-AzApiManagement -ResourceGroupName "ContosoGroup" -Name "ContosoApi"
 PS C:\> $apim.VpnType = "External"
 PS C:\> $apim.VirtualNetwork = $virtualNetwork