Fix Qwen2 importer
<!-- pylint-output-strict-mode-false -->

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---

Your code was analyzed with PyLint. The following annotations have been identified:

```
************* Module nemo.collections.llm.gpt.model.qwen2
nemo/collections/llm/gpt/model/qwen2.py:38:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:56:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:65:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:74:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:84:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:95:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:107:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:127:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/llm/gpt/model/qwen2.py:143:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/llm/gpt/model/qwen2.py:149:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/llm/gpt/model/qwen2.py:176:0: C0115: Missing class docstring (missing-class-docstring)
nemo/collections/llm/gpt/model/qwen2.py:195:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/llm/gpt/model/qwen2.py:212:4: C0116: Missing function or method docstring (missing-function-docstring)
nemo/collections/llm/gpt/model/qwen2.py:216:4: C0116: Missing function or method docstring (missing-function-docstring)

-----------------------------------
Your code has been rated at 9.27/10
```

---

Mitigation guide:

* Add sensible and useful docstrings to functions and methods
* For trivial methods like getter/setters, consider adding `# pylint: disable=C0116` inside the function itself
* To disable multiple functions/methods at once, put a `# pylint: disable=C0116` before the first and a `# pylint: enable=C0116` after the last.

By applying these rules, we reduce the occurance of this message in future.

Thank you for improving NeMo's documentation!
# What does this PR do ?

A simple fix for the Qwen2 importer:

Qwen2 7B and larger require `vocab_size=152064` instead of default `vocab_size=151936`. The `HFQwen2Importer.config` missed this setting.

**Collection**: `llm`

# Usage
* You can potentially add a usage example below

```python
# This usage will fail without this PR
nemo llm import model=qwen2_7b source="hf://Qwen/Qwen2-7B"
python3 ./scripts/llm/generate.py --model_path /root/.cache/nemo/models/Qwen/Qwen2-7B --num_tokens_to_generate 64
```

# Before your PR is "Ready for review"
**Pre checks**:
- [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?
- [ ] 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

## Who can review?
@suiyoubi , since you added Qwen2 to NeMo2