Style removal on using accordionVertical animation

The style attribute should be removed after the animation end when using the accordionVertical animation.
although the style remain with the property `transform-origin` with the value of `"center top 0px"`

It's not gonna make any problem but I think it must be more clear if you remove the style attribute at all.

Thank you.

Start by locating the accordionVertical animation and its animation-end cleanup in the repository. Reproduce the animation and verify that the style attribute, including transform-origin, is removed after it finishes.

Written by the indexing model from the issue text.