Allow 1 ULP on canvas import tests as noted in the comment. (#4697)

src/webgpu/util/texture/color_space_conversions.spec.ts

diff --git a/src/webgpu/util/texture/color_space_conversions.spec.ts b/src/webgpu/util/texture/color_space_conversions.spec.ts
index 56a59ac..37877a6 100644
--- a/src/webgpu/util/texture/color_space_conversions.spec.ts
+++ b/src/webgpu/util/texture/color_space_conversions.spec.ts
@@ -96,7 +96,13 @@
       { x: 0, y: 0, z: 0 },
       { width, height, depthOrArrayLayers: 1 },
       { actTexelView, expTexelView },
-      { maxDiffULPsForNormFormat: 0 }
+      // The canvas 2D side of this comparison is produced by the implementation's color
+      // management system, which typically quantizes to 8 bits internally, so its result
+      // may differ from this file's double-precision reference math by one unit in the
+      // last place. Several of the reference values here land within 0.05/255 of a
+      // round-to-nearest boundary (e.g. display-p3 (0x80, 0, 0x80) converts to an exact
+      // sRGB blue of 132.551/255), so requiring bit-exact agreement is not meaningful.
+      { maxDiffULPsForNormFormat: 1 }
     );
 
     if (failedPixelsMessage !== undefined) {