(fix): fix rlvr get_dataset.

Author: PanAndy

roll/pipeline/rlvr/rlvr_pipeline.py

@@ -14,7 +14,6 @@
 
 from roll.datasets.chat_template import get_chat_template
 from roll.datasets.collator import DataCollatorWithPaddingForPaddedKeys
-from roll.datasets.dataset import get_dataset
 from roll.distributed.executor.cluster import Cluster
 from roll.distributed.scheduler.generate_scheduler import DynamicSamplingScheduler
 from roll.distributed.scheduler.protocol import DataProto