servo: Merge #19138 - Rename js crate to mozjs (from asajeffrey:script-rename-js-dependency-to-mozjs); r=jdm

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This PR renames the `js` dependency to `mozjs', ready for when https://github.com/servo/rust-mozjs/pull/377 lands.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes do not require tests because refactoring

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Source-Repo: https://github.com/servo/servo
Source-Revision: 5b36b74c06232a6436409b5fb474abf271a9e6f7

servo/components/script/lib.rs

@@ -47,8 +47,6 @@ extern crate hyper_serde;
 extern crate image;
 extern crate ipc_channel;
 #[macro_use]
-extern crate js;
-#[macro_use]
 extern crate jstraceable_derive;
 #[macro_use]
 extern crate lazy_static;
@@ -62,6 +60,8 @@ extern crate metrics;
 extern crate mime;
 extern crate mime_guess;
 extern crate mitochondria;
+#[macro_use]
+extern crate mozjs as js;
 extern crate msg;
 extern crate net_traits;
 extern crate nonzero;