Fix for getting tokenizer in character-based ASR models when using tarred dataset
# What does this PR do ?

This PR fixes getting tokenizer in character-based ASR models when using tarred dataset

**Collection**: ASR

# Changelog 
- This PR removed passing `self.tokenizer` to `get_concat_tarred_dataset()` or `get_tarred_dataset()`
  - Because character-based ASR models don't use tokenizers, `self.tokenizer` raises the following error:
```
Traceback (most recent call last):
  File "/workspace/asr/korean/./speech_to_text_rnnt.py", line 85, in main
    asr_model = EncDecRNNTModel(cfg=cfg.model, trainer=trainer)
  File "/workspace/NeMo/nemo/collections/asr/models/rnnt_models.py", line 53, in __init__
    super().__init__(cfg=cfg, trainer=trainer)
  File "/workspace/NeMo/nemo/core/classes/modelPT.py", line 132, in __init__
    self.setup_training_data(self._cfg.train_ds)
  File "/workspace/NeMo/nemo/collections/asr/models/rnnt_models.py", line 563, in setup_training_data
    self._train_dl = self._setup_dataloader_from_config(config=train_data_config)
  File "/workspace/NeMo/nemo/collections/asr/models/rnnt_models.py", line 509, in _setup_dataloader_from_config
    tokenizer=self.tokenizer,
  File "/usr/local/lib/python3.9/site-packages/torch/nn/modules/module.py", line 1207, in __getattr__
    raise AttributeError("'{}' object has no attribute '{}'".format(
AttributeError: 'EncDecRNNTModel' object has no attribute 'tokenizer'
```

# Usage
* You can potentially add a usage example below

```python
# Add a code snippet demonstrating how to use this 
```

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**Pre checks**:
- [ ] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
- [ ] Did you add or update any necessary documentation?
- [ ] Does the PR affect components that are optional to install? (Ex: Numba, Pynini, Apex etc)
  - [ ] Reviewer: Does the PR have correct import guards for all optional libraries?
  
**PR Type**:
- [ ] New Feature
- [X] Bugfix
- [ ] Documentation

If you haven't finished some of the above items you can still open "Draft" PR.


## Who can review?

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# Additional Information
* Related to # (issue)
