Auto merge of #12834 - dtolnay:bound, r=nox

Remove #[serde(bound = "")] attributes

These were fixed in serde_codegen 0.8.0 by serde-rs/serde#456.

cc @nox

- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [x] These changes do not require tests because: the generated code continues to compile

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components/canvas_traits/lib.rs

@@ -74,7 +74,6 @@ pub enum FromLayoutMsg {
 }
 
 #[derive(Clone, Deserialize, Serialize)]
-#[serde(bound = "")] // Prevent serde from generating cyclic bounds.
 pub enum Canvas2dMsg {
     Arc(Point2D<f32>, f32, f32, f32, bool),
     ArcTo(Point2D<f32>, Point2D<f32>, f32),

components/gfx/display_list/mod.rs

@@ -791,7 +791,6 @@ impl fmt::Debug for StackingContext {
 
 /// One drawing command in the list.
 #[derive(Clone, Deserialize, HeapSizeOf, Serialize)]
-#[serde(bound = "")] // Prevent serde from generating cyclic bounds.
 pub enum DisplayItem {
     SolidColorClass(Box<SolidColorDisplayItem>),
     TextClass(Box<TextDisplayItem>),

components/script_traits/script_msg.rs

@@ -59,7 +59,6 @@ pub enum LogEntry {
 
 /// Messages from the script to the constellation.
 #[derive(Deserialize, Serialize)]
-#[serde(bound = "")] // Prevent serde from generating cyclic bounds.
 pub enum ScriptMsg {
     /// Indicates whether this pipeline is currently running animations.
     ChangeRunningAnimationsState(PipelineId, AnimationState),