Update actions to latest versions to avoid Node.js 20 deprecation

Author: tillig

.github/workflows/build.yml

@@ -8,10 +8,10 @@ jobs:
     runs-on: windows-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Setup .NET
-        uses: actions/setup-dotnet@v4
+        uses: actions/setup-dotnet@v5
         with:
           dotnet-version: 10.0.x