Added type annotation to ntbuff in params.py

[manusmad]

Error thrown during import by pydantic since type annotation was missing for field 'ntbuff' in params.py. Simple fix.

import pykilosort
  File "<stdin>", line 1, in <module>
  File "pykilosort/__init__.py", line 12, in <module>
    from .main import run, run_export, run_spikesort, run_preprocess
  File "site-packages/pykilosort/main.py", line 14, in <module>
    from .params import KilosortParams
  File "site-packages/pykilosort/params.py", line 63, in <module>
    class KilosortParams(BaseModel):
  File "site-packages/pydantic/_internal/_model_construction.py", line 95, in __new__
    private_attributes = inspect_namespace(
  File "site-packages/pydantic/_internal/_model_construction.py", line 324, in inspect_namespace
    raise PydanticUserError(
pydantic.errors.PydanticUserError: Field 'ntbuff' requires a type annotation