Comment out imports in the placeholder file

Author: narendasan

torch/_dynamo/backends/tensorrt.py

@@ -1,6 +1,6 @@
-import torch  # type: ignore[import]
-from .common import device_from_inputs, fake_tensor_unsupported  # type: ignore[import]
-from .registry import register_backend  # type: ignore[import]
+# import torch  # type: ignore[import]
+# from .common import device_from_inputs, fake_tensor_unsupported  # type: ignore[import]
+# from .registry import register_backend  # type: ignore[import]
 
 """
 Placeholder for TensorRT backend for dynamo via torch-tensorrt