With http://musicbrainz.org/work/8a9a22ed-1034-4313-8296-abf58efd413d/edit (or any other work with ordered parts) try to unselect "These relationships have a specific ordering" and enter an edit. No edit is actually created.

Not that often there's need to remove ordering, but mistakes happen. For example with this work I used same order as on tracklist but later found out that that the composer never gave any preferred order for performance (he prefers performers to decide).