This is a follow-up to 1e31c41a.
As it turns out the same issue also applied to bitmap images
embedded in the SVG.

Replacing 'cairo_paint_with_alpha()' -> 'cairo_paint()' prevents
reducing opacity when rendering the bitmap onto a cairo surface.

Opacity should already be properly handled in
CairoRenderContext::popLayer()

(cherry picked from commit 1a1d84bd)