fix bloom upsample shaders
fix bloom upsample shaders

We were not using the correct offsets, however because everything
was so blurry, it wasn't obvious that something was wrong.
This should result in a bit smoother bloom effect.
google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament,google/filament