Remove vestigal abortEvent from image attribute.

Remove vestigal abortEvent from image attribute.
https://bugs.webkit.org/show_bug.cgi?id=80795

Reviewed by Adam Barth.

It seems we installed a listener for the abort event on images,
but never ever raised them.  So this patch removes it.  This could
cause different behaviour if the user sends abort events directly
at an image element, although addEventListener will still work.

* html/HTMLImageElement.cpp:
(WebCore::HTMLImageElement::parseAttribute):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@110618 268f45cc-cd09-0410-ab3c-d52691b4dbfc