bug: error when parameter with type hint Any has a default value of None

[rmshaffer]

Describe the bug
A parameter with type hint of Any and a default value of None results in linter error BCS023. (This is related to the new functionality from #17.) However, None is a valid value for a type hint of Any and therefore this should be allowed.

To reproduce
Define a function parameter with a type hint of Any and a default value of None, e.g. previous_value here:

def assign_stmt(target_name: str, value: Any, previous_value: Any = None) -> Any:

results in this error:

BCS023 - Argument 'previous_value' defaults to None but type hint doesn't end with '| None'.

Expected behavior
No error.

Screenshots or logs
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System information
A description of your system. Please provide:

• Python version: 3.9

Additional context
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