test: RemovalNotifier: Increase timeout
test: RemovalNotifier: Increase timeout

The modification notifier will flush its queues after 1s, so wait longer
than 1 or 1.5s before assuming the notification got lost.

This is a weak attempt at fixing some of these tests sporadic failures

chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary,chouquette/medialibrary