Don't update modification date on canceled checkout

[ewohnlich]

plone.app.iterate 4.0.3 (pinned by Plone 5.2.8)

A canceled checkout calls "baseline.reindexObject()" https://github.com/plone/plone.app.iterate/blob/4.0.3/plone/app/iterate/browser/cancel.py#L48 which results in the modification date being updated. I don't think this makes sense - to an end user literally nothing has changed. Unless reindexObject is somehow necessary to trigger relation cleanup, maybe we should pass a value for idxs to this method (reindexObject only updates modification date if idxs==[]). This might already be done by the event listener if I'm following correctly https://github.com/plone/plone.app.iterate/blob/4.0.3/plone/app/iterate/subscribers/locking.py#L56