[WA][conformance][TorchFX] reshape model explicitly (#3229)

Copy of the #3228 to the develop branch

### Changes

TorchFX model in the conformance test are being reshaped explicitly
before the serialization

### Reason for changes

To work around dynamic shapes export OpenVINO bug 161495

### Related tickets

161495

### Tests

job/weekly/job/Daemons/job/PTQ/job/ptq_single_model/7198 - passed

Author: daniil-lyakhov

tests/post_training/pipelines/base.py

@@ -438,6 +438,7 @@ def save_compressed_model(self) -> None:
         elif self.backend == BackendType.FX_TORCH:
             exported_model = torch.export.export(self.compressed_model, (self.dummy_tensor,))
             ov_model = ov.convert_model(exported_model, example_input=self.dummy_tensor.cpu(), input=self.input_size)
+            ov_model.reshape(self.input_size)
             self.path_compressed_ir = self.output_model_dir / "model.xml"
             ov.serialize(ov_model, self.path_compressed_ir)
         elif self.backend == BackendType.ONNX: