Fixed bug where quickupload didn't remove the active class.

`collective.quickupload` sets and removes the `qq-upload-drop-area-active` class.
But it does not remove the class if a file is uploaded.
Normally the dropzone would be hidden after the upload, but with my changes in https://github.com/4teamwork/plonetheme.teamraum/pull/229 the dropzone remains visible.

@lukasgraf