fix: treat explicit tzinfo=None in arrow.get() like an omitted tzinfo

[TrueFurina]

Fixes #1259

Problem: arrow.get() with an explicit tzinfo=None keyword behaves differently from omitting it: the tzinfo key stays in kwargs (only read via get), so the 'tzinfo kwarg is not provided' branch (len(kwargs) == 1 and tz is None) forces arg_count = 3 and crashes, while omitting the kwarg leaves kwargs empty and parses normally.

Fix: pop tzinfo from kwargs so an explicit None and an omitted tzinfo are treated identically (both leave kwargs without the key).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2224255) to head (565a4d0).
✅ All tests successful. No failed tests found.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files           10        10           
  Lines         2315      2315           
  Branches       358       358           
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  Hits          2315      2315           

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