use Node 20 for action

Author: jochenkirstaetter

.github/workflows/dotnetcore.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - name: Setup .NET
-      uses: actions/setup-dotnet@v3
+      uses: actions/setup-dotnet@v4
       with:
         dotnet-version: ${{ matrix.dotnet-version }}
     - name: Build