Two `compressionFuncParams` values are unused

[nick-shaw]

https://github.com/ampas/aces-dev/blob/0b632da885c29f1ca8e816b3995ad5fde976e9ae/lib/Lib.Academy.OutputTransform.ctl#L23

Only [0] and [3] from the array of values get used, with [3] being the 1.0 exponent for powerP. Values [1] and [2] were only ever used in non-reach mode, which is not included in the CTL.

I reality, only a single compressionThreshold value is needed (and it's purpose would be clearer from the name) if the compression curve is simplified to Reinhard.