[All Extensions] Remove explicit WindowsAppSdk reference

[dansiegel]

Current behavior

Currently all Uno.Extensions packages get an explicit reference to Microsoft.WindowsAppSdk.

uno.extensions/src/Directory.Build.targets

Lines 49 to 55 in a3dead4

	<When Condition="$(_IsWinUI)">
	<ItemGroup>
	<PackageReference Include="Microsoft.WindowsAppSDK" Condition="$(WinAppSdkVersion)==''"/>
	<PackageReference Include="Microsoft.WindowsAppSDK" Condition="$(WinAppSdkVersion)!=''" VersionOverride="$(WinAppSdkVersion)"/>
	<PackageReference Include="Microsoft.Windows.SDK.BuildTools" />
	</ItemGroup>
	</When>

Expected behavior

This should come through transitively from Uno.WinUI and only be explicitly provided if there is an explicit reason that we need a newer version.