Auto merge of #18559 - BorisChiou:stylo/animation/shape_outside, r=birtles

Make shape-outside animatable.

We decide to make shape-outside animatable on Gecko, so let's do it on Servo.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix [Bug 1390026](https://bugzilla.mozilla.org/show_bug.cgi?id=1390026).
- [X] These changes do not require tests because we could reuse the animation tests on Gecko for now.

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components/style/properties/longhand/box.mako.rs

@@ -1856,7 +1856,7 @@ ${helpers.predefined_type(
     "generics::basic_shape::ShapeSource::None",
     products="gecko",
     boxed=True,
-    animation_value_type="discrete",
+    animation_value_type="ComputedValue",
     flags="APPLIES_TO_FIRST_LETTER",
     spec="https://drafts.csswg.org/css-shapes/#shape-outside-property",
 )}