Incorrect PIECE_VALUE used for multiplication of knights on the evaluate function

[tolumide-ng]

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Hello, Thank you for your hard work and dedication to this project! I really appreciate the effort that goes into maintaining it. I encountered an issue I think might have been an unintended typo on the evaluate function in position.rs here: https://github.com/dede1751/carp/blob/91a609f2747a1746502fb1dc2183ed495841bbb4/engine/src/position.rs#L153

It appears that the PIECE_VALUE of a king was used to multiply the knights count.

Thanks again for your time.