Auto merge of #25240 - pshaughn:unspecial_mouseover, r=SimonSapin

Took out the special mouseover cancel case

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eventtarget.rs was checking the event type to see if it was a mouseover; now it doesn't. Other special-case events like error and beforeunload go down other code paths entirely, so this one has no special cases left.

---
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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 #25190

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- [X] There are tests for these changes

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tests/wpt/metadata/html/webappapis/scripting/events/event-handler-processing-algorithm.html.ini

@@ -3,16 +3,3 @@
   [beforeunload listener returning null cancels event]
     bug: https://github.com/servo/servo/issues/10787
     expected: FAIL
-
-  [mouseover listener returning false cancels event (using Event)]
-    expected: FAIL
-
-  [mouseover listener returning false cancels event (using MouseEvent)]
-    expected: FAIL
-
-  [mouseover listener returning true doesn't cancel event (using Event)]
-    expected: FAIL
-
-  [mouseover listener returning true doesn't cancel event (using MouseEvent)]
-    expected: FAIL
-