Change comments for improved consistency (#5223)

* Change comments for improved consistency

https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md#L56
https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md#L80
https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md#L87

* updating DIRECTORY.md

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