Update objectives.py so uses kge instead of 1-kge

[Ben-Choat]

I think as an artifact of previous times when all optimization was done via minimization, if a user wanted to optimize using 'kling_gupta', they would have to specify 'min' as target. This is completely counterintuitive since kge should be maxmized (-inf<kge<=1 and kge=1 is best possible score). By using kge direclty, the user can intuitively set the target as 'max'.

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[hellkite500]

I think this is something we need to do, but I would like to keep the ability to effectively "minimize" kge using this technique. Perhaps a new function with a distinct name which inverts the KGE range would be best. Then kge could be used as the original kling_gupta_efficiency without the need of a wrapper function.