Remove unneeded triggering of event

The "droppedOnTrash" event was being triggered when the file list was
initialized, but it should be triggered only when the user actually
drops a file on the trash bin.

Besides that, the event had no effect; only the file list handles it,
but as it was not triggered on any element it ended being triggered on
the document, and thus not handled. Moreover, even if it had been
triggered on the file list it would have been done before the handler
was set, so it would not have been handled anyway. And even if it had
been handled no data was provided, so the handler would have failed.

In conclusion, triggering the event there was not needed, and thus it
was removed.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>