Don't add output directory twice when creating shared sentencepiece tokenizer
Signed-off-by: Patrick Simianer <patrick@lilt.com>

# What does this PR do ?

As the title says this is a small fix: The output dir was already added to `encoder_tokenizer_model` on line 789 in the same file.

**Collection**: NLP

# Changelog 
- Bugfix for creating shared sentencepiece tokenizer.

# Usage

The error can be triggered by running preprocessing with NeMo for an MT data set:
```
#!/bin/bash

python ../nemo/examples/nlp/machine_translation/enc_dec_nmt.py \
  -cn aayn_base \
  do_training=false \
  model.preproc_out_dir=./preproc_dir/ \
  model.train_ds.use_tarred_dataset=true \
  model.train_ds.lines_per_dataset_fragment=1000000 \
  model.train_ds.num_batches_per_tarfile=200 \
  model.train_ds.src_file_name=../europarl-v7.de-en.en \
  model.train_ds.tgt_file_name=../europarl-v7.de-en.de \
  model.validation_ds.src_file_name=../valid.en \
  model.validation_ds.tgt_file_name=../valid.de \
  model.encoder_tokenizer.vocab_size=32000 \
  model.decoder_tokenizer.vocab_size=32000 \
  model.encoder_tokenizer.library=sentencepiece \
  model.encoder_tokenizer.training_sample_size=9999 \
  model.decoder_tokenizer.library=sentencepiece \
  model.decoder_tokenizer.training_sample_size=9999 \
  ~model.test_ds \
  trainer.accelerator='cpu' \
  +trainer.fast_dev_run=true \
  exp_manager=null
```

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- [x] Make sure you read and followed [Contributor guidelines](https://github.com/NVIDIA/NeMo/blob/main/CONTRIBUTING.md)
- [ ] Did you write any new necessary tests?
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**PR Type**:
- [ ] New Feature
- [x] Bugfix
- [ ] Documentation

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# Additional Information
