Update WinUIMajorVersion to 3 in build scripts

Author: Arlodotexe

Build-Toolkit-Components.ps1

@@ -85,7 +85,7 @@ Param (
     [hashtable]$AdditionalProperties,
 
     [Alias("winui")]
-    [int]$WinUIMajorVersion = 2,
+    [int]$WinUIMajorVersion = 3,
 
     [string]$ComponentDir = "src",
 

Build-Toolkit-Gallery.ps1

@@ -69,7 +69,7 @@ Param (
   [hashtable]$AdditionalProperties,
 
   [Alias("winui")]
-  [int]$WinUIMajorVersion = 2,
+  [int]$WinUIMajorVersion = 3,
 
   [Alias("c")]
   [string[]]$Components = @("all"),

GenerateAllSolution.ps1

@@ -46,7 +46,7 @@ Param (
     [string[]]$Components = @('all'),
 
     [Alias("winui")]
-    [int]$WinUIMajorVersion = 2,
+    [int]$WinUIMajorVersion = 3,
 
     [string[]]$ExcludeComponents,