Auto merge of #15187 - montrivo:webidl-exposed, r=jdm

Partial - Expose interfaces only where they should be. #12415

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Reviewed webidl interfaces:

Location.webidl
MediaError.webidl
MimeTypeArray.webidl
MimeType.webidl
PageTransitionEvent.webidl
PluginArray.webidl
Plugin.webidl
PopStateEvent.webidl

---
<!-- 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
- [ ] These changes fix #12415 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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tests/wpt/mozilla/tests/mozilla/interfaces.worker.js

@@ -32,14 +32,9 @@ test_interfaces([
   "Headers",
   "History",
   "ImageData",
-  "MediaError",
   "MessageEvent",
-  "MimeType",
-  "MimeTypeArray",
   "Performance",
   "PerformanceTiming",
-  "Plugin",
-  "PluginArray",
   "ProgressEvent",
   "Request",
   "Response",