Update type hints

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 89.90%. Comparing base (19ea3cd) to head (065f59b).

Files	Patch %	Lines
foamlib/_dictionaries/_base.py	80.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #74 +/- ## ========================================== - Coverage 90.06% 89.90% -0.16% ========================================== Files 8 8 Lines 755 763 +8 ========================================== + Hits 680 686 +6 - Misses 75 77 +2 ```

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