Remove .NET 8 support

Author: rnelson

.github/workflows/dotnet.yml

@@ -20,7 +20,6 @@ jobs:
       uses: actions/setup-dotnet@v5
       with:
         dotnet-version: |
-          8.0.x
           9.0.x
           10.0.x
     - name: Restore dependencies

KeysExportViewer/KeysExportViewer.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net10.0-windows;net9.0-windows;net8.0-windows</TargetFrameworks>
+    <TargetFrameworks>net10.0-windows;net9.0-windows</TargetFrameworks>
     <OutputType>WinExe</OutputType>
     <PublishUrl>publish\</PublishUrl>
     <Install>true</Install>