Update tree_delete_min_applyold.vpr test case to new magic wand syntax

[viper-admin]

Created by @alexanderjsummers on 2019-08-28 10:02

The file uses now as a construct; this doesn’t exist in recent Viper. Instead, one should use e.g. labelled-old expressions referring to a label just before the package statement.

See https://github.com/viperproject/silicon/issues/187 for more information.