Time Complexity: Update the worst-case scenario example

[Maddily]

Because

The previous explanation overlooked the worst-case scenario when the element we're looking for is the last one in the array.

This PR

• Updates the worst-case explanation to make sure it covers both possible cases: when the item isn't found and when the item is the last one in the array.

Issue

Closes #28903

Additional Information

N/A

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[JoshDevHub]

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