fix(sorts): raise ValueError on negative inputs in radix_sort (#14950)

[nalin1012]

Fixes #14950

Describe your change:

Added input validation to sorts/radix_sort.py to raise a ValueError when negative integers are passed in list_of_ints. Included doctest examples verifying both normal execution and the expected ValueError.

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
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• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
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