servo: Merge #11824 - Use get_mut instead of get-remove-set in XHR send() (from DarinM223:master); r=KiChjang

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Mutates the header directly with get_mut instead of using get(), remove(), and set().
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<!-- 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 #11811  (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because there are existing web tests

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Source-Repo: https://github.com/servo/servo
Source-Revision: a3f43076b6b30491dcb4d9b8cc1ae32261a82f99

servo/components/msg/Cargo.toml

@@ -15,7 +15,7 @@ cssparser = {version = "0.5.4", features = ["heap_size", "serde-serialization"]}
 euclid = "0.7.1"
 heapsize = "0.3.0"
 heapsize_plugin = "0.1.2"
-hyper = {version = "0.9", features = ["serde-serialization"]}
+hyper = {version = "0.9.9", features = ["serde-serialization"]}
 ipc-channel = {git = "https://github.com/servo/ipc-channel"}
 layers = {git = "https://github.com/servo/rust-layers", features = ["plugins"]}
 plugins = {path = "../plugins"}