servo: Merge #20404 - GamepadButtonList::sync_from_vr should use more iterators #20392 (from MaximilianDauner:issue_20392); r=jdm

<!-- Please describe your changes on the following line: -->
Used the zip function instead of iterating over both vectors with an indexing variable and using unwrap.

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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 fix #20392(github issue number if applicable).

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- [x] These changes do not require tests because it says in the issue description no need for tests
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Source-Repo: https://github.com/servo/servo
Source-Revision: 5a432eaad33f36591f62c3d2671ffd9956be3594

--HG--
extra : subtree_source : https%3A//hg.mozilla.org/projects/converted-servo-linear
extra : subtree_revision : 4aa46a5256c0be438435e5f72af0f2b3468fd97e

servo/components/script/dom/gamepadbuttonlist.rs

@@ -37,10 +37,8 @@ impl GamepadButtonList {
     }
 
     pub fn sync_from_vr(&self, vr_buttons: &[WebVRGamepadButton]) {
-        let mut index = 0;
-        for btn in vr_buttons {
-            self.list.get(index).as_ref().unwrap().update(btn.pressed, btn.touched);
-            index += 1;
+        for (gp_btn, btn) in self.list.iter().zip(vr_buttons.iter()) {
+            gp_btn.update(btn.pressed, btn.touched);
         }
     }
 }