Improve Test Coverage with Doctests for Floyd Warshall algorithm

[Yashcodes04]

Describe your change:

This pull request adds comprehensive doctests to functions within an existing file to improve test coverage and ensure functionality reliability. The updates are designed to better demonstrate and verify the functionality of the algorithms through direct examples within the docstrings.

• [ ] Add an algorithm?
• [ ] Fix a bug or typo in an existing algorithm?
• [x] Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• [ ] Documentation change?

Checklist:

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized.
• [x] I know that pull requests will not be merged if they fail the automated tests.
• [x] This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• [x] All new Python files are placed inside an existing directory.
• [x] All filenames are in all lowercase characters with no spaces or dashes.
• [x] All functions and variable names follow Python naming conventions.
• [x] All function parameters and return values are annotated with Python type hints.
• [x] All functions have doctests that pass the automated testing.
• [ ] All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• [ ] If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

Contributes to #9943

Additional Notes:

This pull request contributes to the ongoing efforts to enhance code quality by increasing the number of doctests across the project, thereby improving the accuracy and reliability of the algorithm implementations.