Update dotnetcore.yml

Author: maliming

.github/workflows/dotnetcore.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v4
         with:
-          dotnet-version: 8.0.x
+          dotnet-version: 9.0.x
       - name: Build with dotnet
         run: dotnet build -c Release
       - name: Test with dotnet