[MNT] Replace Live Server Calls with Mocks in Unit Tests #1649

Several tests currently rely on direct connections to the live server (production/test), which can cause race conditions, server overload, and sporadic failures (see #1586). To ensure these remain true unit tests, they should use mocks/patches instead of the remote server.

Steps:

1. Identify tests using the remote server, e.g., marked with "production_server" or "test_server".
2. Mock or patch requests.Session in tests relying on openml._api_calls._send_request. Alternatively, higher-level mocking can be used to simplify implementation.

Affected test files (can be separate sub-tasks/PRs):

• test_datasets/test_dataset_functions.py
• test_datasets/test_dataset.py
• test_evaluations/test_evaluation_functions.py
  • [MNT] Replace live server call with mock in test_evaluation_list_filter_run #1672
• test_flows/test_flow_functions.py
  • [MNT] Replace live server calls with mocks in test_list_flows (test_flows/test_flow_functions.py) #1670
• test_flows/test_flow.py
• test_openml/test_api_calls.py
• test_runs/test_run_functions.py
• test_runs/test_run.py
• test_runs/test_trace.py
• test_setups/test_setup_functions.py
  • [MNT] Replace live server call with mock in test_setup_list_filter_flow (test_setups/test_setup_functions.py) #1673
  • [MNT] Replace live server calls with mocks in test_setup_functions.py #1674
• test_study/test_study_functions.py
  • [MNT]Replaced Live Test-Server Calls with Mocks in Unit Tests on tests/test_study/test_study_function.py module #1668
• test_tasks/test_classification_task.py
• test_tasks/test_clustering_task.py
  • [MNT] Replace live server calls with mocks in test_clustering_task.py #1669
• test_tasks/test_learning_curve_task.py
  • Mock test_class_labels in test_learning_curve_task.py #1675
• test_tasks/test_regression_task.py
• test_tasks/test_supervised_task.py
• test_tasks/test_task_functions.py
• test_tasks/test_task_methods.py
  • [MNT] Replace live server calls with mocks in test_task_methods.py #1664
• test_tasks/test_task.py
• test_utils/test_utils.py