Remove redundant schema overrides in #71

Job	Run time
image (base/base-disk-x86_64)	41m 33s
docker (base/base-docker-x86_64)	18m 1s
live-iso (flagship/flagship-live)	34m 20s
image (base/base-disk-aarch64)	53m 47s
docker (base/base-docker-aarch64)	20m 51s
live-iso (gnome/gnome-live)	31m 39s
live-iso (kde/kde-live)	35m 37s
live-iso (pantheon/pantheon-live)	34m 55s
docker-push	1m 9s
push-live-iso	1s
	4h 31m 53s

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