fix github workflow

Author: Gramli

.github/workflows/dotnet.yml

@@ -22,7 +22,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v3
         with:
-          dotnet-version: 7.0.x
+          dotnet-version: 9.0.x
       - name: Restore dependencies
         run: dotnet restore
       - name: Build