Fix bytes to GB conversion for logged VRAM usage (#19254)

Signed-off-by: Mohammed Yasin <32206511+Y-T-G@users.noreply.github.com>
Co-authored-by: UltralyticsAssistant <web@ultralytics.com>

ultralytics/engine/trainer.py

@@ -493,7 +493,7 @@ class BaseTrainer:
             memory = 0
         else:
             memory = torch.cuda.memory_reserved()
-        return memory / 1e9
+        return memory >> (2**30)
 
     def _clear_memory(self):
         """Clear accelerator memory on different platforms."""