Auto merge of #11370 - Ms2ger:IterableContext, r=jdm

Remove the IterableContext trait.

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [x] `./mach build -d` does not report any errors
- [x] `./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 refactoring

Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process.

It serves no purpose.

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="35" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/11370)
<!-- Reviewable:end -->

components/script/script_thread.rs

@@ -33,7 +33,7 @@ use dom::bindings::refcounted::{LiveDOMReferences, Trusted};
 use dom::bindings::str::DOMString;
 use dom::bindings::trace::JSTraceable;
 use dom::bindings::utils::WRAP_CALLBACKS;
-use dom::browsingcontext::{BrowsingContext, IterableContext};
+use dom::browsingcontext::BrowsingContext;
 use dom::document::{Document, DocumentProgressHandler, DocumentSource, FocusType, IsHTMLDocument};
 use dom::element::Element;
 use dom::event::{Event, EventBubbles, EventCancelable};