Fix `torch.amp` has no attribute `GradScaler` (#14647)

Co-authored-by: UltralyticsAssistant <web@ultralytics.com>

ultralytics/engine/trainer.py

@@ -41,7 +41,6 @@ from ultralytics.utils.checks import check_amp, check_file, check_imgsz, check_m
 from ultralytics.utils.dist import ddp_cleanup, generate_ddp_command
 from ultralytics.utils.files import get_latest_run
 from ultralytics.utils.torch_utils import (
-    TORCH_1_13,
     EarlyStopping,
     ModelEMA,
     autocast,
@@ -266,11 +265,7 @@ class BaseTrainer:
         if RANK > -1 and world_size > 1:  # DDP
             dist.broadcast(self.amp, src=0)  # broadcast the tensor from rank 0 to all other ranks (returns None)
         self.amp = bool(self.amp)  # as boolean
-        self.scaler = (
+        self.scaler = torch.cuda.amp.GradScaler(enabled=self.amp)
-            torch.amp.GradScaler("cuda", enabled=self.amp)
-            if TORCH_1_13
-            else torch.cuda.amp.GradScaler(enabled=self.amp)
-        )
         if world_size > 1:
             self.model = nn.parallel.DistributedDataParallel(self.model, device_ids=[RANK], find_unused_parameters=True)