[docs] Link to `loadeddata` event is incorrect

[bicarlsen]

Describe the Bug

The Window.onloadeddata docs link to MDN docs points to https://developer.mozilla.org/en-US/docs/Web/API/Window/onload which is 404.

I believe the correct link is: https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/loadeddata_event