fix: array element wrongly used as array index

[ChaituBoi]

Description of Change

Incorrect logic using array element as array index in maxSubArray().

Checklist

• [ x] Added description of change
• [x ] Relevant documentation/comments is changed or added
• [ x] PR title follows semantic commit guidelines
• [ x] Search previous suggestions before making a new one, as yours may be a duplicate.
• [ x] I acknowledge that all my contributions will be made under the project's license.

Notes:

[ChaituBoi]

Hello, this is my first time contributing to any open source project. I am amazed at the collection of algorithms here and would be happy to contribute. Thank you and apologies for anything wrong.

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[github-actions]

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