Auto merge of #11769 - splav:master, r=jdm

Remove unused XHR method

<!-- Please describe your changes on the following line: -->
Remove unused XHR method.
---
<!-- 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` does not report any errors
- [X] These changes fix #11760 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because it is a cleanup

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components/script/dom/xmlhttprequest.rs

@@ -1041,12 +1041,6 @@ impl XMLHttpRequest {
         self.response_status.set(Ok(()));
     }
 
-    fn insert_trusted_header(&self, name: String, value: String) {
-        // Insert a header without checking spec-compliance
-        // Use for hardcoded headers
-        self.request_headers.borrow_mut().set_raw(name, vec![value.into_bytes()]);
-    }
-
     fn dispatch_progress_event(&self, upload: bool, type_: Atom, loaded: u64, total: Option<u64>) {
         let global = self.global();
         let progressevent = ProgressEvent::new(global.r(),