Update GWO.py

[Kahina-ainseur]

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[RaneemQaddoura]

Dear @Kahina-ainseur,

Thank you for your contribution.

The equation you have changed will cause the value to decrease from 2 to -2 instead of 2 to 0, as per the paper of GWO [1]. Do you have another reason for changing it?

[1] Mirjalili, S., Mirjalili, S. M., & Lewis, A. (2014). Grey wolf optimizer. Advances in engineering software, 69, 46-61.