fit function in src/common/trainer.py does not use the saved parameter

Additionally the docstring lists it as default: True, when the actual function defaults to false.
```
def fit(self, train_data, valid_data=None, test_data=None, saved=False, verbose=True):
    r"""Train the model based on the train data and the valid data.

    Args:
        ...
        saved (bool, optional): whether to save the model parameters, default: True
```