feat: Add greedy_coin_change.py algorithm (#3805)

* Hacktoberfest: Add greedy_coin_change.py file 

added the file in greedy_methods folder to implement the same method

Altered the code according to the changes that were requested.

* Added doctests.

doctests added to the function find_minimum_change.

* Added Greedy change file in Maths folder.

* updating DIRECTORY.md

* Deleted Greedy Method Folder

* updating DIRECTORY.md

* Update greedy_coin_change.py

* fix: black formatting issues

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>