Originally, `this` was set to `E['currentTarget']` which, based on the MDN doc linked in preactjs#2166, certainly sounds like the correct thing to do.  A couple years later it was changed to `never` in preactjs#3147 with no commentary on the PR or commit indicating why.  My guess is that this was changed so arrow functions would work, which I believe are permanently bound and cannot be rebound by the caller.

I believe that `never` is wrong because this code doesn't compile:
```ts
type TargetedEvent<Target extends EventTarget = EventTarget, TypedEvent extends Event = Event> = Omit<TypedEvent, 'currentTarget'> & { readonly currentTarget: Target }
interface EventHandler<E extends TargetedEvent> {
	(this: never, event: E): void
}
declare const apple: EventHandler<TargetedEvent<HTMLElement, Event>>
declare const event: TargetedEvent<HTMLElement, Event>
apple(event) // error TS2684: The 'this' context of type 'void' is not assignable to method's 'this' of type 'never'.
```
Changing to `void` resolves this error and should work everywhere I believe.

I removed the comment since it no longer applies with this being `never` or `void`.  It appears that it was just forgotten when the switch from `E['currentTarget']` to `never` was made.

* Changes `EventHandler<...>` to have a `this` of type `void`.

Originally, `this` was set to `E['currentTarget']` which, based on the MDN doc linked in #2166, certainly sounds like the correct thing to do.  A couple years later it was changed to `never` in #3147 with no commentary on the PR or commit indicating why.  My guess is that this was changed so arrow functions would work, which I believe are permanently bound and cannot be rebound by the caller.

I believe that `never` is wrong because this code doesn't compile:
```ts
type TargetedEvent<Target extends EventTarget = EventTarget, TypedEvent extends Event = Event> = Omit<TypedEvent, 'currentTarget'> & { readonly currentTarget: Target }
interface EventHandler<E extends TargetedEvent> {
	(this: never, event: E): void
}
declare const apple: EventHandler<TargetedEvent<HTMLElement, Event>>
declare const event: TargetedEvent<HTMLElement, Event>
apple(event) // error TS2684: The 'this' context of type 'void' is not assignable to method's 'this' of type 'never'.
```
Changing to `void` resolves this error and should work everywhere I believe.

I removed the comment since it no longer applies with this being `never` or `void`.  It appears that it was just forgotten when the switch from `E['currentTarget']` to `never` was made.

* Removes incorrectly passing test.

The type signature's intent is to make it clear to users that they cannot rely on `this` being the element in callbacks, and they should use `event.currentTarget` instead.  This test was testing that the user could unwisely ignore that.

---------

Co-authored-by: Jovi De Croock <decroockjovi@gmail.com>