Add insertion sort complexity details

[Sushanth012]

Summary

• Add best, average, and worst case time complexity to the insertion_sort docstring
• Add constant auxiliary space complexity to the same docstring

Closes #14866

Tests

• py -3.14 -m doctest -v sorts\insertion_sort.py
• uvx ruff@0.15.15 check sorts\insertion_sort.py
• uvx ruff@0.15.15 format --check sorts\insertion_sort.py

[algorithms-keeper]

Closing this pull request as invalid

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