[sp] clean up imports (#4878)

Author: hjh0119

swift/trainers/sequence_parallel/ulysses.py

@@ -15,7 +15,6 @@
 from torch.nn import CrossEntropyLoss
 from torch.utils.data import DataLoader, Sampler
 from trl.extras.profiling import profiling_decorator
-from trl.trainer.grpo_trainer import RepeatSampler
 
 from swift.llm import DataLoaderDispatcher, DataLoaderShard, get_llm_model, to_device
 from swift.utils import get_current_device, get_device, get_dist_setting, seed_worker