Remove redundant `nn.log_softmax` in `run_flax_glue.py`
# What does this PR do?

`optax.softmax_cross_entropy` expects unscaled logits, so it already calls `nn.log_softmax` ([here](https://github.com/deepmind/optax/blob/master/optax/_src/loss.py#L166)). `nn.log_softmax` is idempotent so mathematically it shouldn't have made a difference.

## Before submitting
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      Pull Request section?
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- [ ] Did you write any new necessary tests?

## Who can review?

@marcvanzee @patrickvonplaten 

Great catch @n2cholas! Could you also remove the line:

```python
import flax.linen as nn
```

to make our code quality checks happy? Happy to merge right after :-)<|||||>Done @patrickvonplaten!