Auto merge of #14370 - thiagopnts:master, r=Wafflespeanut

use Either type for UrlOrNone

Use the Either type for UrlOrNone

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #14298 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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tests/unit/style/properties/serialization.rs

@@ -418,9 +418,9 @@ mod shorthand_serialization {
     }
 
     mod list_style {
-        use style::properties::longhands::list_style_image::SpecifiedValue as ListStyleImage;
         use style::properties::longhands::list_style_position::computed_value::T as ListStylePosition;
         use style::properties::longhands::list_style_type::computed_value::T as ListStyleType;
+        use style::values::Either;
         use super::*;
 
         #[test]
@@ -428,7 +428,7 @@ mod shorthand_serialization {
             let mut properties = Vec::new();
 
             let position = DeclaredValue::Value(ListStylePosition::inside);
-            let image = DeclaredValue::Value(ListStyleImage::Url(
+            let image = DeclaredValue::Value(Either::First(
                 SpecifiedUrl::new_for_testing("http://servo/test.png")));
             let style_type = DeclaredValue::Value(ListStyleType::disc);