[6.x] Fix bug with wildcard caching in event dispatcher

[driesvints]

    Event::listen('foo', fn () => dump('foo listener'));
    Event::listen('foo*', fn () => dump('foo* listener'));
    Event::dispatch('foo');

    Event::forget('foo');
    Event::forget('foo*');
    Event::dispatch('foo');

The above code would still execute the foo* listener because it will still be cached. We'll need to clear the cache when we forget the given (wildcard) key.

Fixes #31307