Update nuget.yaml

Author: spewu

.github/workflows/nuget.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: 7.x
+          dotnet-version: 8.x
 
       - name: Publish NuGet
         uses: likvido/action-nuget@v1