Update ci.yml

Author: thebentern

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v3
       with:
-        dotnet-version: 8.0.x
+        dotnet-version: 9.0.x
 
     - name: Restore dependencies
       run: dotnet restore