[BUG] Type Hint issue with `studies` functions

[nachomaiz]

Describe the bug
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bavapi.studies and bavapi.Client.studies have the wrong type annotation for year_numbers. It is typing.Optional[int] but should be bavapi.typing.OptionalListOr[int]

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• OS: [e.g. Windows]
• IDE [e.g. Jupyter, VSCode]
• Version [e.g. 22]

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[nachomaiz]

Fixed in #3