(maint) Update documentation generation script

When working on this, some irregularities were noted with the generation
of the documentation, so these changes avoid the issues that arose.

update-cmdlet-documentation.ps1

@@ -1,4 +1,6 @@
-<#
+# PowerShell Core generates additional documentation that may not be correct for running under Windows PowerShell.
+#Requires -PSEdition Desktop
+<#
 .SYNOPSIS
 Generates Markdown documentation for the Chocolatey.PowerShell portion of Chocolatey's installer module commands.
 
@@ -85,12 +87,12 @@ if (-not (Get-Module Chocolatey.PowerShell)) {
     throw "The Chocolatey.PowerShell module was not able to be loaded, exiting documentation generation."
 }
 
-$newOrUpdatedFiles = [System.Collections.Generic.HashSet[System.IO.FileSystemInfo]] @(
+$newOrUpdatedFiles = @(
     if ($NewCommand) {
-        New-MarkdownHelp -Command $NewCommand -OutputFolder "$PSScriptRoot\docs" -ExcludeDontShow
+        New-MarkdownHelp -Command $NewCommand -OutputFolder $documentationPath -ExcludeDontShow
     }
 
-    Update-MarkdownHelp -Path $documentationPath -ExcludeDontShow
+    Update-MarkdownHelp -Path $documentationPath -ExcludeDontShow | Where-Object BaseName -ne $NewCommand
 )
 
 $incompleteFiles = $newOrUpdatedFiles | Select-String '\{\{[^}]+}}' | Select-Object -ExpandProperty Path