Update UWP projects to .NET 9 stable tools

Author: Sergio0694

build/Directory.Build.props

@@ -59,12 +59,6 @@
       since in order to use these APIs the caller already has to be in an unsafe context.
     -->
     <NoWarn>$(NoWarn);CS8500</NoWarn>
-
-    <!--
-      We are using the UWP support for .NET 9, which is currently in preview. The warning from the .NET 9 SDK
-      about this feature being in preview is unnecessary and it just produces a lot of noise, so we can disable it.
-    -->
-    <NoWarn>$(NoWarn);NETSDK1219</NoWarn>
   </PropertyGroup>
 
   <!-- Centralized location for all generated artifacts -->

samples/ComputeSharp.SwapChain.D2D1.Uwp/ComputeSharp.SwapChain.D2D1.Uwp.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>WinExe</OutputType>
-    <TargetFramework>net8.0-windows10.0.22621.0</TargetFramework>
+    <TargetFramework>net9.0-windows10.0.22621.0</TargetFramework>
     <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
     <WindowsSdkPackageVersion>10.0.22621.57</WindowsSdkPackageVersion>
     <UseUwp>true</UseUwp>

samples/ComputeSharp.SwapChain.Uwp/ComputeSharp.SwapChain.Uwp.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>WinExe</OutputType>
-    <TargetFramework>net8.0-windows10.0.26100.0</TargetFramework>
+    <TargetFramework>net9.0-windows10.0.26100.0</TargetFramework>
     <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
     <WindowsSdkPackageVersion>10.0.26100.57</WindowsSdkPackageVersion>
     <UseUwp>true</UseUwp>