In the viewport, semi-transparent strokes could appear more yellowish.
This was because the `reveal_tx` uses the `GPU_R11F_G11F_B10F` format
(loosing precision in the blue channel).
Now using `GPU_RGB10_A2` for `reveal_tx` to fix the issue.
We don't need to change the format for the `color_tx`.
Pull Request: https://projects.blender.org/blender/blender/pulls/141335