[Touch.Client] Use 'BundledNETCoreAppTargetFrameworkVersion' in TargetFramework to avoid having to bump every year. (#122)

Touch.Client/dotnet/MacCatalyst/Touch.Client-MacCatalyst.dotnet.csproj

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net8.0-maccatalyst</TargetFramework>
+    <TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-maccatalyst</TargetFramework>
   </PropertyGroup>
   <Import Project="../shared.csproj" />
 </Project>

Touch.Client/dotnet/iOS/Touch.Client-iOS.dotnet.csproj

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net8.0-ios</TargetFramework>
+    <TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-ios</TargetFramework>
   </PropertyGroup>
   <Import Project="../shared.csproj" />
 </Project>

Touch.Client/dotnet/macOS/Touch.Client-macOS.dotnet.csproj

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net8.0-macos</TargetFramework>
+    <TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-macos</TargetFramework>
   </PropertyGroup>
   <Import Project="../shared.csproj" />
 </Project>

Touch.Client/dotnet/tvOS/Touch.Client-tvOS.dotnet.csproj

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net8.0-tvos</TargetFramework>
+    <TargetFramework>net$(BundledNETCoreAppTargetFrameworkVersion)-tvos</TargetFramework>
     <!-- Currently, NuGet is not able to restore existing Xamarin.TVOS packages for a .NET 5 project, so use AssetTargetFallback to tell NuGet that the existing packages work -->
     <AssetTargetFallback>xamarintvos10;$(AssetTargetFallback)</AssetTargetFallback>
   </PropertyGroup>