Fix CI build

Now that platyPS requirement is actually checked.

Author: andyleejordan

.vsts-ci/templates/ci-general.yml

@@ -48,6 +48,7 @@ steps:
     script: |
       Get-Module -ListAvailable Pester
       Install-Module InvokeBuild -Scope CurrentUser -Force
+      Install-Module platyPS -Scope CurrentUser -Force
       Invoke-Build -Configuration Release
       Write-Host "##vso[task.setvariable variable=vsixPath]$(Resolve-Path powershell-*.vsix)"
     workingDirectory: $(Build.SourcesDirectory)/vscode-powershell