fix: remove memory leak `get_size_of_linked_list.cpp`

[vil02]

Description of Change

get_size_of_linked_list.cpp has a memory leak. This PR adds the function deleteList in order to fix it.

Checklist

• [x] Added description of change
• [x] Added file name matches File name guidelines
• [x] ~Added tests and example, test must pass~
• [x] Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
• [x] Relevant documentation/comments is changed or added
• [x] PR title follows semantic commit guidelines
• [x] Search previous suggestions before making a new one, as yours may be a duplicate.
• [x] I acknowledge that all my contributions will be made under the project's license.

Notes:

Removes memory leak in get_size_of_linked_list.cpp.

[github-actions[bot]]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[vil02]

@Panquesito7, @realstealthninja: please dont-close.