examples/event-test: Fix remove return type
examples/event-test: Fix remove return type

The remove function are supposed to return 0 on success and -1 on failure.
<https://libvirt.org/html/libvirt-libvirt-event.html#virEventRemoveTimeoutFunc>

Signed-off-by: Philipp Hahn <8cb7a2c205789112a9f61bc3102305826b6a8db1@univention.de>

libvirt/libvirt-python,libvirt/libvirt-python,libvirt/libvirt-python