Fix invalid code formatting
Due to the pre-commit breakage fixed in 25a0f123 (CI/tests: Update pre-commit docker image and apply code formatting, 2024-04-09) some invalid formatted code slipped in via 39e64d52 (Fix get_server_class_list for case if there is no Dserver device or n_classes=0, add tests for both cases, 2024-04-12).
Fix that.