Update build_and_test.yml for net9

Author: fdonnet

.github/workflows/build_and_test.yml

@@ -26,7 +26,7 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v4
       with:
-        dotnet-version: 8.0.x
+        dotnet-version: 9.0.x
 
     - name: Restore dependencies
       run: dotnet restore