Use TypeError for non-string input in count_vowels (#14196)

* Use TypeError for non-string input in count_vowels

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* Fix docstring and improve input validation in kth_lexicographic_permutation

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update kth_lexicographic_permutation.py

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Maxim Smolskiy <[email protected]>