Update .NET version in CI workflow

Remove commented out .NET version 5.0.x from CI workflow.

Author: sdrapkin

.github/workflows/ci.yml

@@ -26,7 +26,6 @@ jobs:
         uses: actions/setup-dotnet@v5
         with:
           dotnet-version: |
-#            5.0.x
             6.0.x
             7.0.x
             8.0.x