Expect canonical capitalization in transform functions

CSS Transforms requires transform functions to serialize according to their individual grammars. The scaleX, scaleY, scaleZ, skewX, and skewY grammars retain the uppercase axis letter, but ten parsing assertions currently expect lowercase function names.

Correct those expected names while preserving the existing input and numeric serialization coverage.

https://drafts.csswg.org/css-transforms-1/#serialization-of-transform-functions
https://drafts.csswg.org/css-transforms-2/#three-d-transform-functions

Co-authored-by: codex <codex@openai.com>

css/css-transforms/parsing/transform-valid.html

diff --git a/css/css-transforms/parsing/transform-valid.html b/css/css-transforms/parsing/transform-valid.html
index b436fbd..ee57fb4 100644
--- a/css/css-transforms/parsing/transform-valid.html
+++ b/css/css-transforms/parsing/transform-valid.html
@@ -38,14 +38,14 @@
 test_valid_value("transform", "scale(-250%)", "scale(-2.5)");
 test_valid_value("transform", "scale(-500%, -620%)", "scale(-5, -6.2)");
 
-test_valid_value("transform", "scaleX(7)", "scalex(7)");
-test_valid_value("transform", "scaleX(720%)", "scalex(7.2)");
+test_valid_value("transform", "scaleX(7)", "scaleX(7)");
+test_valid_value("transform", "scaleX(720%)", "scaleX(7.2)");
 
-test_valid_value("transform", "scaleY(-8)", "scaley(-8)");
-test_valid_value("transform", "scaleY(-85%)", "scaley(-0.85)");
+test_valid_value("transform", "scaleY(-8)", "scaleY(-8)");
+test_valid_value("transform", "scaleY(-85%)", "scaleY(-0.85)");
 
-test_valid_value("transform", "scaleZ(4)", "scalez(4)");
-test_valid_value("transform", "scaleZ(25%)", "scalez(0.25)");
+test_valid_value("transform", "scaleZ(4)", "scaleZ(4)");
+test_valid_value("transform", "scaleZ(25%)", "scaleZ(0.25)");
 
 test_valid_value("transform", "scale3d(0.5, 2.5, 3)");
 test_valid_value("transform", "scale3d(50%, 250%, 300%)", "scale3d(0.5, 2.5, 3)");
@@ -62,11 +62,11 @@
 test_valid_value("transform", "skew(0, -90deg)", "skew(0deg, -90deg)");
 test_valid_value("transform", "skew(90deg, 0)", ["skew(90deg)", "skew(90deg, 0deg)"]);
 
-test_valid_value("transform", "skewX(0)", "skewx(0deg)");
-test_valid_value("transform", "skewX(90deg)", "skewx(90deg)");
+test_valid_value("transform", "skewX(0)", "skewX(0deg)");
+test_valid_value("transform", "skewX(90deg)", "skewX(90deg)");
 
-test_valid_value("transform", "skewY(0)", "skewy(0deg)");
-test_valid_value("transform", "skewY(-90deg)", "skewy(-90deg)");
+test_valid_value("transform", "skewY(0)", "skewY(0deg)");
+test_valid_value("transform", "skewY(-90deg)", "skewY(-90deg)");
 
 test_valid_value("transform", "perspective(10px)");
 test_valid_value("transform", "perspective(none)");