Horizon removed the Django-based implementation of launch instance [1]
which was overriden by cloudkitty-dashboard. Remove override to avoid
breaking Horizon when cloudkitty-dashboard is enabled.
[1] https://review.opendev.org/c/openstack/horizon/+/816303
Change-Id: Ib6516cfb4d9bbe75ddb62969f62629712afca38b
Story: 2009924
Task: 44788