Blender Git Loki

Palettes: Remove threshold parameter when extract from images

Using a number greater than 1 produce a huge number of entries in the palette because any small variation in the color create a new entry.

Remove the threshold reduce the precision of the color extracted, but always is better than having a palette with thounsands of colors.

Related to T78317

Still pending the memory crash when it's impossible to allocate memory for the palette in the popover, but with this change I don't think we get this error again.