Copy-paste error in tagger implementation

[ZhanruiLiang]

Describe the bug
Code location:
https://github.com/jacksonllee/pycantonese/blob/main/src/pycantonese/pos_tagging/tagger.py#L262
From the context, i+2 should be used but it has i-2 currently.
I tried to fix and and regen the model pickle file, but that fails some tests which I don't know how to proceed.

To reproduce

• Change i-2 to i+2 in the linked line and the line below.
• Regenerate model by running train_tagger.py
• Run tests `python -m pytest tests/test_parsing.py

Expected behavior
All tests pass.

System (please complete the following information):

• Operating System: MacOS
• PyCantonese version: 3.4.0

[jacksonllee]

I've resolved this issue at the main branch. Some of the tests got upset due to noise in the training data from HKCanCor -- that's been fixed as well.

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