Revert "ONNX export tool: output dim sizes only when model is RF"

This reverts commit 4785332.

This is unclear to me.
This should not be necessary.
There likely is some other bug somewhere.

tools/export_to_onnx.py

@@ -174,14 +174,7 @@ def main():
         model_outputs_raw_keys.append(k)
         for i, dim in enumerate(v.dims):
             if dim.is_batch_dim() or dim.is_dynamic():
-                # For PyTorch we usually don't have the output dimensions as Dim
-                # classes available in the final tensor, so we can't call
-                # mark_as_default_output(shape=(batch_dim, ...)).
-                # These dimensions are automatically instantiated to actual values when
-                # the output tensor is passed as parameter to mark_as_default_output
-                # without any shape. Therefore, we don't add these to the output.
-                if is_rf_module:
-                    model_outputs_raw_keys.append(f"{k}:size{i}")
+                model_outputs_raw_keys.append(f"{k}:size{i}")
 
     dynamic_axes = {}
     for k, v in list(extern_data.data.items()) + list(model_outputs.data.items()):