Zh_TN files names for char

[BuyuanCui]

What does this PR do ?

Add a one line overview of what this PR aims to accomplish. Changes include changing the class char to word. This means the python files in tagger, verbalizer and tests are changed.

• tagger/char.py -> word.py
• verbalizer/char.py -> word.py
• tests/zh/test_cases_char.txt -> test_cases_word.txt
• tests/zh/test_char.py -> test_word.py

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Pre checks:

• [ *] Have you signed your commits? Use git commit -s to sign.
• [ *] Do all unittests finish successfully before sending PR? 1) pytest or (if your machine does not have GPU) pytest --cpu from the root folder (given you marked your test cases accordingly @pytest.mark.run_only_on('CPU')). 2) Sparrowhawk tests bash tools/text_processing_deployment/export_grammars.sh --MODE=test ...
• [ ] If you are adding a new feature: Have you added test cases for both pytest and Sparrowhawk here.
• [ *] Have you added __init__.py for every folder and subfolder, including data folder which has .TSV files?
• [ *] Have you followed codeQL results and removed unused variables and imports (report is at the bottom of the PR in github review box) ?
• [ *] Have you added the correct license header Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved. to all newly added Python files?
• [ *] If you copied nemo_text_processing/text_normalization/en/graph_utils.py your header's second line should be Copyright 2015 and onwards Google, Inc.. See an example here.
• [ *] Remove import guards (try import: ... except: ...) if not already done.
• [ ] If you added a new language or a new feature please update the NeMo documentation (lives in different repo).
• [ ] Have you added your language support to tools/text_processing_deployment/pynini_export.py.

PR Type:

• [ ] New Feature
• [ *] Bugfix
• [ ] Documentation
• [ ] Test

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