Auto merge of #25254 - pshaughn:stop_creating_outofspec_events, r=jdm

Removed createEvent cases, removed now-unused new_uninitializeds

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document.createEvent was creating some event types WHATWG now says shouldn't be created that way. This was the only caller of a few new_uninitialized methods, so those are removed too.

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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 #25137

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- [X] There are tests for these changes

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