Update breadth_first_search_2.py (#7765)

* Cleanup the BFS

* Add both functions and timeit

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

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* Add performace results as comment

* Update breadth_first_search_2.py

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