test-renderers: Update tone mapping images.

When working on commit 1e68913,
I neglected to note that there were `*-wgpu.png` images already present.
By updating them, we can set the comparison thresholds lower.
Of course, it would be better if there wasn’t a difference between
renderers, but I still don’t have any theories about why there is this
particular one.

test-renderers/src/test_cases.rs

@@ -937,17 +937,11 @@ async fn tone_mapping(mut context: RenderTestContext, (tmo, exposure): (ToneMapp
         context.universe(),
     );
 
-    // TODO: Ideally there would be at most 1 difference but there are large-enough-to-be-visible
-    // ones for some reason. These appeared, not when working on the tone mapping algorithm, but
-    // when changing PackedLight’s rounding behavior.
-    // Also, there is a notable ray/wgpu difference concentrated in the middle range of Reinhard.
+    // TODO: There is a notable ray/wgpu difference concentrated in the middle range of Reinhard.
     // So, there are probably bugs lurking here.
+    // (The thresholds here are *not* for those difference but other pixel differences.)
     context
-        .render_comparison_test(
-            Threshold::new([(20, 200), (10, 500), (3, 2000), (2, 20000)]),
-            scene,
-            Overlays::NONE,
-        )
+        .render_comparison_test(Threshold::new([(10, 100), (3, 500)]), scene, Overlays::NONE)
         .await;
 }