Auto merge of #13528 - UK992:test-geckolib, r=Manishearth

Fix `test-geckolib`

This will make Travis green again.

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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 it's only cleanup

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tests/unit/stylo/lib.rs

@@ -4,7 +4,6 @@
 
 extern crate app_units;
 extern crate cssparser;
-extern crate gecko_bindings;
 extern crate style;
 extern crate style_traits;