Auto merge of #11359 - servo:ScriptControlChan, r=Manishearth

Remove the unused ScriptControlChan type.

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy --faster` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

Either:
- [ ] There are tests for these changes OR
- [x] These changes do not require tests because removing dead code

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components/script_traits/lib.rs

@@ -338,10 +338,6 @@ pub struct InitialScriptState {
     pub content_process_shutdown_chan: IpcSender<()>,
 }
 
-/// Encapsulates external communication with the script thread.
-#[derive(Clone, Deserialize, Serialize)]
-pub struct ScriptControlChan(pub IpcSender<ConstellationControlMsg>);
-
 /// This trait allows creating a `ScriptThread` without depending on the `script`
 /// crate.
 pub trait ScriptThreadFactory {