fix: make bubble sort work with comparable items

[nikhiltumma]

Describe your change

Fix bubble sort comparisons to use the lt operation defined by the Comparable protocol.

Tests:

• python sorts/bubble_sort.py
• python -m doctest -v sorts/bubble_sort.py

All 42 doctests pass.

Fixes #15234

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

Checklist

• I have read https://github.com/TheAlgorithms/Python/blob/master/CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• 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".

[cclauss]

@priya-sundaram-dev, please review.

[cclauss]

Probably better to change the types to match the algorithm rather than vise versa, but let's go for it.