Update dotnet-version to 9.x

Author: ddidgdimitrov-infragistics

.github/workflows/build-test-ci.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Setup .NET
         uses: actions/setup-dotnet@v3
         with:
-          dotnet-version: '6.x'
+          dotnet-version: '9.x'
 
       - name: Restore dependencies
         run: dotnet restore