Update test for positive inchikey

[tongyu0924]

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Description

This PR adds a positive test for the _is_inchikey function in the CompoundIdentifier class. The new test ensures that valid InChIKeys return True as expected, improving the identifier validation logic.

Changes to be made

• Added a new test function test_is_inchikey_positive using @pytest.mark.parametrize.
• Ensured that the test covers multiple valid InChIKey examples.
• Confirmed all tests pass locally with pytest.

Status

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To do

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Is this pull request related to any open issue? If yes, replace issueID below with the issue ID

Related to #1319

[DhanshreeA]

I will look into why pytest-benchmark is complaining. @Abellegese any quick guesses?

[Abellegese]

Hi @DhanshreeA I think the PR has been created before my improvement merged so with the new compound identifier, we need smiles in that function. I guess.