Removes update of pwsh since appveyor images are updated (#1084)

appveyor.yml

@@ -19,16 +19,6 @@ cache:
 install:
   - ps:   if ($env:PowerShellEdition -eq 'WindowsPowerShell') { Import-Module .\tools\appveyor.psm1; Invoke-AppveyorInstall }
   - pwsh: if ($env:PowerShellEdition -eq 'PowerShellCore')    { Import-Module .\tools\appveyor.psm1; Invoke-AppveyorInstall }
-  - ps:   |
-            # Windows image still has version 6.0.0 of pwsh but 6.0.2 is required due to System.Management.Automation package https://github.com/appveyor/ci/issues/2230
-            if ($env:PowerShellEdition -eq 'PowerShellCore' -and $PSVersionTable.PSVersion -lt [version]'6.0.2' -and $IsWindows) {
-                $msiPath = "$env:TEMP\PowerShell-6.0.2-win-x64.msi"
-                (New-Object Net.WebClient).DownloadFile('https://github.com/PowerShell/PowerShell/releases/download/v6.0.2/PowerShell-6.0.2-win-x64.msi', $msiPath)
-                Write-Verbose 'Installing pwsh 6.0.2' -Verbose
-                Start-Process 'msiexec.exe' -Wait -ArgumentList "/i $msiPath /quiet"
-                Remove-Item $msiPath
-                $env:Path = "$env:ProgramFiles\PowerShell\6.0.2;$env:Path"
-            }
 
 build_script:
   - ps:   |