Remove OS selection condition (#8284)

images.CI/linux-and-win/convert-to-vhd.ps1

@@ -95,10 +95,6 @@ $targetKey = az storage account keys list `
 Write-Host ("Copying VHD blob from '{0}' to 'https://{1}.blob.core.windows.net/{2}/{3}'..." `
     -f $sourceDiskUri.Split('?')[0], $StorageAccountName, $StorageAccountContainerName, $VhdName)
 
-if ($env:OS) {
-  $sourceDiskUri = """{0}""" -f $sourceDiskUri
-}
-
 az storage blob copy start `
   --source-uri $sourceDiskUri `
   --destination-blob $VhdName `