This option was deprecated in Ussuri [1] as nova no longer provided any
schedulers aside from the filter scheduler and the existence of
third-party schedulers was very unlikely. Stop configuring this and
simply use the default.
[1] https://review.opendev.org/#/c/707225/
Change-Id: Iabdd1d00e00ee269334f0fe0db265a97207e2dc6
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>