Blender Git Loki

Fix T85261: Eevee passes have slight inaccurate colors

In everything in `EEVEE_renderpasses_postprocess` (or the corresponding
renderpass_postprocess_frag.glsl) colors get divided by a
'currentSample'.

This 'currentSample' is always incremented in
`EEVEE_temporal_sampling_draw` (and also one more time before we reach
`EEVEE_renderpasses_postprocess`.
This results in a "off-by-one", slightly inacurate colors and slight
inaccurate transparency (in certain passes like AOVs).

Now decrement the currentSample `EEVEE_renderpasses_postprocess` again
by one to compensate.

Maniphest Tasks: T85261

Differential Revision: https://developer.blender.org/D10286