opengl/colormanagement: also clip after tonemapping
With night light, the maximum luminance that can be represented in the buffer without color shifts is lower than the value represented by 1.0. When writing into the buffer, OpenGL implicitly clips for us to 1.0, so we end up with an out of bounds value, which ends up causing color shifts when the result is converted to a different white point.
To avoid that, explicitly clip to the maximum luminance after tonemapping.