Type: set the output transform in main's new shadow-filter test frame

Main added uncached_darkness_shadow_subtracts_before_separate_opacity, which builds a Frame
without the output field this branch adds, so the merged tree did not compile.

crates/render/src/fx/renderer.rs

@@ -716,6 +716,7 @@ mod tests {
             px: 1.0,
             opts: &opts,
             ink: Ink::Display,
+            output: Affine::IDENTITY,
         };
         let mut ctx = frame.offscreen_context(100, 100);
         let mut r = Renderer::new();