Use DxWrapper's gamma shader

[BC46]

The latest version of DxWrapper comes with a gamma shader that allows the in-game gamma slider to work in (borderless) windowed mode. However, I disabled it for the time being because the HDE installer automatically enables a gamma shader from ReShade if any of the windowed mode options are enabled. I didn't want to tinker with the installer code just before release. Though it's better to use the DxWrapper gamma shader because it works without the use of ReShade as well.

Since dgVoodoo doesn't have a gamma shader, people who select this graphics API in combination with the windowed modes will still need the ReShade shader.