Update longest_increasing_subsequence.py

[squenson1]

Counter-example that doesn't return the longest increasing subsequence

Describe your change:

The algorithm longest_increasing_subsequence.py has a bug for the sequence [28, 26, 12, 23, 35, 39] as it returns [26, 35, 39] instead of [12, 23, 35, 39]. (No change in code has been done).

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

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[MaximSmolskiy]

@squenson1 Thanks for counter-example.

In future, please create issues for such problems (as I created #12510) - not pull requests.

Additionally, I found a problem in current doctest

>>> longest_subsequence([9, 8, 7, 6, 5, 7])
[8]

Correct answers could be [7, 7], [6, 7] or [5, 7]

I am closing this pull request - feel free to fix current incorrect implementation and create corresponding pull request.