fix typos in FSDP config parsing logic in `TrainingArguments` (#29189)

fix FSDP config

src/transformers/training_args.py

@@ -1732,9 +1732,9 @@ class TrainingArguments:
                         os.environ[f"{prefix}TRANSFORMER_CLS_TO_WRAP"] = ",".join(
                             self.fsdp_config["transformer_layer_cls_to_wrap"]
                         )
-            prefetch_policy = self.fsdp_config.get("fsdp_backward_prefetch", "NO_PREFETCH")
+            prefetch_policy = self.fsdp_config.get("backward_prefetch", "NO_PREFETCH")
             os.environ[f"{prefix}BACKWARD_PREFETCH"] = prefetch_policy.upper()
-            os.environ[f"{prefix}FORWARD_PREFETCH"] = self.fsdp_config.get("forward_prefect", "false")
+            os.environ[f"{prefix}FORWARD_PREFETCH"] = self.fsdp_config.get("forward_prefetch", "false")
             os.environ[f"{prefix}SYNC_MODULE_STATES"] = self.fsdp_config.get("sync_module_states", "true")
             os.environ[f"{prefix}USE_ORIG_PARAMS"] = self.fsdp_config.get("use_orig_params", "true")