Remove Windows 2019 and Ubuntu 20.04 files and reference (#13533)

helpers/GenerateResourcesAndImage.ps1

@@ -1,11 +1,10 @@
 $ErrorActionPreference = 'Stop'
 
 enum ImageType {
-    Windows2019   = 1
-    Windows2022   = 2
-    Windows2025   = 3
-    Ubuntu2204    = 4
-    Ubuntu2404    = 5
+    Windows2022   = 1
+    Windows2025   = 2
+    Ubuntu2204    = 3
+    Ubuntu2404    = 4
 }
 
 Function Get-PackerTemplate {
@@ -18,10 +17,6 @@ Function Get-PackerTemplate {
 
     switch ($ImageType) {
         # Note: Double Join-Path is required to support PowerShell 5.1
-        ([ImageType]::Windows2019) {
-            $relativeTemplatePath = Join-Path (Join-Path "windows" "templates") "build.windows-2019.pkr.hcl"
-            $imageOS = "win19"
-        }
         ([ImageType]::Windows2022) {
             $relativeTemplatePath = Join-Path (Join-Path "windows" "templates") "build.windows-2022.pkr.hcl"
             $imageOS = "win22"
@@ -88,7 +83,7 @@ Function GenerateResourcesAndImage {
         .PARAMETER ResourceGroupName
             The name of the resource group to store the resulting artifact. Resource group must already exist.
         .PARAMETER ImageType
-            The type of image to generate. Valid values are: Windows2019, Windows2022, Windows2025, Ubuntu2204, Ubuntu2404.
+            The type of image to generate. Valid values are: Windows2022, Windows2025, Ubuntu2204, Ubuntu2404.
         .PARAMETER ManagedImageName
             The name of the managed image to create. The default is "Runner-Image-{{ImageType}}".
         .PARAMETER AzureLocation