test: verify insertion sort modifies input collection

[SwetaKumari7]

Description

Add a doctest to verify that insertion_sort modifies the input collection in place and returns the same collection.

Changes

• Verify that the returned object is the original collection.
• Verify that the original collection is sorted after the function call.

Testing

• python -m doctest -v sorts/insertion_sort.py
• python -m ruff check sorts/insertion_sort.py

Both checks pass.

[cclauss]

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

• https://hacktoberfest.com