Add clear_least_significant_set_bit operation

[deerred643-star]

Describe your change

This PR adds clear_least_significant_set_bit(), which uses
number & (number - 1) to clear the rightmost set bit. The docstring explains
the bitwise operation and includes doctests for zero, powers of two, multiple
set bits, and negative integers under Python's sign-extension semantics.

• 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?

Tests

• python -m doctest -v bit_manipulation/single_bit_manipulation_operations.py
• ruff check bit_manipulation/single_bit_manipulation_operations.py
• ruff format --check bit_manipulation/single_bit_manipulation_operations.py

Checklist

• I have read 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".

Fixes #12970

[cclauss]

ON HOLD: Our focus is on merging or closing old pull requests before October 1st.

• https://hacktoberfest.com

[priya-sundaram-dev]

LGTM. Clean, well-scoped addition — the n & (n - 1) trick to clear the least significant set bit is exactly right, and I like that the docstring explains why it works rather than just asserting it.

I verified it independently: ran the doctests (21/21 pass) and cross-checked n & (n-1) against n - (n & -n) (subtracting the lowest set-bit value) for positives, negatives, zero, and powers of two (0, 8, 15, 44, 255, 256, -5, -1, -256) — all match, including the two's-complement negative cases your -5 -> -6 doctest covers.

Type hints and doctests are present per the contributing guide. One tiny, non-blocking nit: the linked reference is the Kernighan bit-counting kernel; it uses the same n & (n-1) identity so it's relevant, but a reader might expect a page specifically about clearing the low bit. Fine to leave as-is.

Approving.