Update knapsack.py (#7271)

* Update knapsack.py

* Update dynamic_programming/knapsack.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update knapsack.py

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Co-authored-by: Christian Clauss <cclauss@me.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>