This make the shadow rays always multiply the lighting,
which can make renders with large light sources darker.
This bias introduced too many light leaking issues. And
these issues are made more visible since the introduction
of 410282e156.
Its first use was to avoid self shadowing artifacts from
large light sources. Since the shading was already
integrated over the visible hemisphere, it made sense
that the shadowing was also in the visible hemisphere.
However this only works if the shading is actually
clipped to the visible hemisphere above the geometric
normal, which might not always be the case.
Given it is better to have self shadowing noise than
light leaking, it is better to just removing this trick.
Self shadow noise can be mitigated by increasing the
sample count or by increasing the terminator bias.
Light leaking, on the other hand, has no known workaround.
Fix#136594
Pull Request: https://projects.blender.org/blender/blender/pulls/137485
b01cdf7df2