tests: fix test_fts_distributed_compat on MacOS

lightning raises the following error when initializing the Trainer:

ValueError: You set `strategy=ddp` but strategies from the DDP family
are not supported on the MPS accelerator. Either explicitly set
`accelerator='cpu'` or change the strategy.

Signed-off-by: Ihar Hrachyshka <[email protected]>

Author: booxter

tests/test_finetuning_scheduler_callback.py

@@ -2468,7 +2468,7 @@ def test_fts_invalid_schedules(tmpdir, invalid_schedules, schedule_key: str, exp
     "strategy, devices, accelerator, strategy_conf, results_key",
     [
         pytest.param("test_strategy", 1, "auto", "stgy_allow_untest", "allow_untest"),
-        pytest.param("ddp", 1, "auto", "stgy_disallow_untest", "disallow_untest", marks=RunIf(skip_windows=True)),
+        pytest.param("ddp", 1, "cpu", "stgy_disallow_untest", "disallow_untest", marks=RunIf(skip_windows=True)),
         pytest.param("test_strategy", 1, "cpu", "cust_stgy_adapter_found", "cust_stgy_adapter_found"),
         pytest.param("test_strategy", 1, "cpu", "cust_stgy_adapter_not_found", "cust_stgy_adapter_not_found"),
         pytest.param("test_strategy", 1, "cpu", "cust_stgy_adapter_not_importable", "cust_stgy_adapter_not_importable"),