Disable jitter noise during evaluation in SwitchTransformers
Author: DaizeDong
Pull request: yes

# What does this PR do?

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The jitter noise was mistakenly added during evaluation in GPTSanJapanese and SwitchTransformers, which would bring uncertainty to the evaluation results. Now the bug is fixed, and the implementation is the same as the [native code](https://github.com/tensorflow/mesh/blob/e6798a2610a2c2f4c4cd236d8214422cb1ecc00a/mesh_tensorflow/transformer/moe.py#L903-L905) of switch transformers.

The former implementation is:

```python
if self.jitter_noise > 0:
    # Multiply the token inputs by the uniform distribution - adding some noise
    hidden_states *= torch.empty_like(hidden_states).uniform_(1.0 - self.jitter_noise, 1.0 + self.jitter_noise)
```

The fixed implementation is:

```python
if self.training and self.jitter_noise > 0:
    # Multiply the token inputs by the uniform distribution - adding some noise
    hidden_states *= torch.empty_like(hidden_states).uniform_(1.0 - self.jitter_noise, 1.0 + self.jitter_noise)
```

This PR also updates the outdated annotations in `configuration_switch_transformers.py`. Now the default values in the annotation area are the same as the values in the `__init__` for SwitchTransformersConfig.


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Comments:
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